JP2009042446A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of suppressing color mixing and prolonging a time period during which the light source emits light. <P>SOLUTION: The field sequential liquid crystal display device (display device) 100 is equipped with a plurality of display pixels 22 including a liquid crystal 224 and LEDs 26 as the light source, and is configured in such a way that voltages corresponding to image signals are sequentially written in respective display pixels 22 after a voltage producing the slowest response speed of the liquid crystal 224 is simultaneously applied to all the display pixels 22 within a frame period, and the LEDs 26 are turned on after the lapse of a predetermined time period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly, to a display device including a plurality of display pixels including liquid crystal.

  Conventionally, as a display method of a liquid crystal display device, red image writing, red backlight emission, green image writing, green backlight emission, blue image writing, and blue backlight emission are sequentially performed in one frame period. There is known a display device that performs display by a field sequential method in which a color image is recognized by an afterimage phenomenon of human eyes (see, for example, Patent Document 1).

  In the field sequential liquid crystal display device described in Patent Document 1, the screen area of the display device is divided for each predetermined number of pixel rows, and each of the divided screen area regions includes a plurality of RGB. A light source is arranged. Then, for each divided screen region, video data is written in red (R), green (G), and blue (B) and displayed by light emission of the light source (display by a field sequential method). As a result, light is emitted from the screen area where the writing of the video data has been completed, so that it is possible to lengthen the time during which the light source emits light in the entire screen area. As a result, the display of the field sequential liquid crystal display device can be brightened.

Japanese Patent Laid-Open No. 2002-221702

  However, since the field sequential liquid crystal display device described in Patent Document 1 is configured to be driven by the field sequential method for each divided screen region, for example, a red light source emits light in one screen region. However, when light sources of different colors emit light, such as when a green light source emits light in the other screen region, there is a problem that color mixture due to light leakage occurs at the boundary portion of each screen region.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a display device capable of suppressing color mixing and extending the time during which a light source emits light. Is to provide.

Means for Solving the Problems and Effects of the Invention

  A display device according to one aspect of the present invention includes a plurality of display pixels including a liquid crystal and a backlight as a light source, and after applying a predetermined voltage to all the display pixels simultaneously within one frame period, A voltage corresponding to the video signal is sequentially written to each display pixel, and then the backlight is turned on after a predetermined time has elapsed.

  In the display device according to one aspect of the present invention, as described above, a predetermined voltage is simultaneously applied to all the display pixels before sequentially writing the voltage corresponding to the video signal to each display pixel within one frame period. For example, if a voltage with the slowest response speed of the liquid crystal is applied as the predetermined voltage, all the display pixels simultaneously start responding to the predetermined voltage with the slowest response speed of the liquid crystal. At the same time, the response to each video signal is started sequentially from the display pixel in which the voltage corresponding to the video signal is written. As a result, when the voltage corresponding to the video signal is sequentially written, the display pixels to be written in the latter half are simultaneously applied to all the pixels when the voltage corresponding to the video signal is written. Since the response to the application of the predetermined voltage is almost completed, the response to the writing of the voltage corresponding to the video signal is started from the state where the response to the predetermined voltage with the slowest response speed of the liquid crystal is almost completed. Can do. In this case, even if the voltage corresponding to the video signal is the voltage with the slowest response of the liquid crystal, the voltage with the slowest response of the liquid crystal has already been written and the response of the liquid crystal has been completed. It is unnecessary. In addition, when the voltage corresponding to the video signal is a voltage other than the voltage with the slowest response speed, the liquid crystal response is completed faster than the response to the voltage with the slowest liquid crystal response speed. The response time of the liquid crystal can be shortened. As a result, since the response period of the liquid crystal after writing to the display pixel where writing is performed in the latter half can be shortened, the lighting time of the backlight can be lengthened. As a result, the display device The display can be brightened. In addition, the voltage corresponding to the video signal is sequentially written to each display pixel, and the backlight is turned on after a certain period of time, so that the writing of the voltage corresponding to the video signal to all the display pixels is completed. Since the backlight is turned on later, it is possible to suppress the simultaneous emission of a plurality of light sources, unlike the case where RGB light sources are emitted for each pixel region. Therefore, color mixing can be suppressed from occurring in a pixel region where a plurality of display pixels are arranged.

  In the display device according to the above aspect, it is preferable that, after a predetermined voltage is applied to all the display pixels all at once, when the voltage corresponding to the video signal is sequentially written to each display pixel, the same gradation is applied. In the display pixel for displaying the display pixel, the response speed of the display pixel written in the second half is configured to be faster than the response speed of the display pixel written in the first half. According to this configuration, the display pixel written in the second half has a shorter period until the response is completed as compared with the display pixel written in the first half, and accordingly, after all the display pixels are written. The period until the response as the entire display pixel is completed can be shortened. As a result, the light emission time of the backlight can be extended, and the display on the display device can be brightened.

  In the display device according to the above aspect, it is preferable that the voltage applied to all the display pixels all at once is a voltage at which the response speed of the liquid crystal is the slowest. With this configuration, when the writing of the display pixel that is written in the second half is started, the slowest voltage of the liquid crystal is already written to the display pixel that is written in the second half, and the response of the liquid crystal is completed. Therefore, it is possible to easily shorten the response period of the liquid crystal after the writing to the display pixel in which writing is performed in the latter half is completed.

  In the display device according to the above aspect, the voltage applied to all the display pixels simultaneously is an off voltage. With this configuration, for example, when the voltage with the slowest response speed of the liquid crystal is the off voltage, the voltage with the slowest response speed of the liquid crystal is simultaneously applied to all the display pixels only by applying the off voltage. Can be easily written.

  In the display device according to the above aspect, preferably, the liquid crystal is a normally white display that transmits light in a state where an off voltage is applied, and the constituent molecules are bowed after a voltage that causes phase transition of the liquid crystal is applied. The voltage applied to all the display pixels simultaneously is a voltage corresponding to a video signal for displaying white. With this configuration, since the liquid crystal is normally white display, writing that displays white with the slowest response speed of the liquid crystal is performed simultaneously on all display pixels only by applying an off voltage. be able to. In addition, by configuring the liquid crystal molecules to bend after applying a voltage that causes phase transition of the liquid crystal, the change in the orientation of the liquid crystal molecules is accelerated by the bending of the bow. The response speed with respect to writing of the voltage corresponding to the signal can be increased.

  In the display device according to the above aspect, preferably, the liquid crystal is a normally black display that does not transmit light in a state where an off-voltage is applied, and the constituent molecules are bowed after a voltage that causes phase transition of the liquid crystal is applied. The voltage applied to all the display pixels simultaneously is a voltage corresponding to a video signal for displaying black. With this configuration, when the liquid crystal is normally black, only by applying an off voltage, a response to display the slowest black of the liquid crystal at the same time is started for all display pixels. Therefore, it is possible to easily control all display pixels. Also, by applying a voltage that causes the liquid crystal to undergo phase transition, the liquid crystal constituent molecules are configured to bend, so that the change in the orientation of the liquid crystal molecules is accelerated by the bending of the bow. The response speed with respect to writing of the voltage corresponding to the signal can be increased.

  In the display device according to the above aspect, the backlight is preferably formed of a light emitting diode element. With this configuration, the space required for the arrangement is reduced as compared with the case where a fluorescent lamp is used for the backlight, so that the apparatus main body can be reduced in size accordingly.

  In the display device according to the above aspect, the backlight is preferably configured by three light emitting diode elements corresponding to RGB, and when displaying an image, the three light emitting diode elements corresponding to RGB are colored. It is configured to be controlled by field sequential driving that is controlled so as to light up in turn every time. With this configuration, in a method of obtaining a desired color by spatially displaying red (R), green (G), and blue (B) and mixing them, one pixel is divided into three for each color. On the other hand, in field sequential driving, since each color is turned on in turn, it is not necessary to divide one pixel into three. Therefore, the aperture ratio can be increased correspondingly, and the display on the display unit can be brightened.

  In the display device according to the above aspect, it is preferable that, when displaying an image, the backlight is controlled by impulse driving that blinks at predetermined time intervals. If comprised in this way, when an image | video is displayed by impulse drive, it controls so that an image blinks by a predetermined time interval, Therefore It can suppress that an afterimage remains in a retina. Thereby, the display performance of a moving image can be improved.

  In the display device according to the above aspect, it is preferable that the period during which writing is performed by applying a predetermined voltage to all the display pixels all at once is shorter than the period during which the voltage corresponding to the video signal is sequentially written into each display pixel. It is comprised so that it may become. With this configuration, even if an operation for performing writing by applying a predetermined voltage to all the display pixels at once is added, the operation for simultaneous writing is applied rather than a size in which the entire operation period becomes longer. As a result, the shortened size of the entire response period becomes larger, so that the response period of the display pixels can be shortened as a whole.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing an overall configuration of a field sequential liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a configuration of a display pixel according to the first embodiment of the present invention. First, the configuration of the field sequential liquid crystal display device 100 according to the first embodiment will be described with reference to FIGS. 1 and 2. In the first embodiment, a case where the present invention is applied to a field sequential liquid crystal display device 100 which is an example of a display device will be described.

  As shown in FIG. 1, the field sequential liquid crystal display device 100 according to the first embodiment includes a drive unit 1 and a display unit 2. This will be described in detail below.

  As shown in FIG. 1, the drive unit 1 includes an A / D converter 11, a PLL (phase synchronization) circuit 12, a memory control unit 13, a memory 14, an analog driver 15, a timing control circuit 16, and a level. A conversion circuit 17, an LED control circuit 18, and a microcomputer unit 19 are included.

  The A / D converter 11, the PLL circuit 12, and the memory control unit 13 are connected. The A / D converter 11 has a function of converting an analog video signal into a digital signal of R (red), G (green), and B (blue). The PLL circuit 12 has a function of generating a clock to be written to the memory 14 from the horizontal synchronization signal and generating a clock necessary for field sequential driving. The memory control unit 13 also has a function of generating a timing signal for storing the video signal converted into the RGB digital signal in the memory 14 for each RGB, and generating a timing signal for calling necessary for field sequential driving. .

  The A / D converter 11 and the memory control unit 13 are connected to the memory 14. The memory 14 has a function of storing RGB digital signals.

  The analog driver 15 is connected to the memory 14. The analog driver 15 has a function of reading out RGB digital signals stored in the memory 14 and converting them into RGB analog signals and supplying the RGB analog signals to the display unit 2.

  The timing control circuit 16 is connected to the memory 14, the level conversion circuit 17, and the LED control circuit 18. The timing control circuit 16 has a function of generating a timing signal for driving a display pixel 22 described later. The level conversion circuit 17 has a function of generating pulses (horizontal / vertical control signals, field sequential drive control signals) for driving the display pixels 22. Further, the LED control circuit 18 has a function of controlling light emission and light emission stop of the LED 26 described later in accordance with the timing of field sequential driving.

  The microcomputer unit 19 is connected to all circuits included in the drive unit 1 (not shown), and has a function of controlling the operation of the entire drive unit 1.

  As shown in FIG. 1, the display unit 2 includes a substrate 21, a plurality of display pixels 22, an H driver 23 and a V driver 24 connected to the plurality of display pixels 22, and an H driver 23 and a V driver 24. And an LED (light emitting diode element) 26 (26a to 26c) that emits red (R), green (G), and blue (B) as a backlight of the display pixel 22. Has been. The LED 26 is an example of the “backlight” in the present invention.

  Further, as shown in FIG. 2, a plurality of signal lines 31 and a plurality of scanning lines 32 are arranged on the substrate 21 so as to be orthogonal to each other. The signal line 31 is connected to the H driver 23, and the scanning line 32 is connected to the V driver 24. Display pixels 22 are arranged at positions where the signal lines 31 and the scanning lines 32 intersect. FIG. 2 shows only the configuration for four pixels for the sake of simplicity. Each display pixel 22 includes an n-channel transistor 221, a pixel electrode 222, a common electrode 223 disposed opposite to the pixel electrode 222, a liquid crystal 224 sandwiched between the pixel electrode 222 and the common electrode 223, and an auxiliary And a capacitor 225. The drain region D of the n-channel transistor 221 is connected to the signal line 31, and the source region S is connected to the pixel electrode 222 and one electrode of the auxiliary capacitor 225. The gate G of the n-channel transistor 221 is connected to the scanning line 32. The liquid crystal 224 is subjected to a parallel rubbing process (a process for aligning liquid crystal molecule groups in a certain direction), and a retardation plate and a polarizing plate (not shown) are arranged.

  FIG. 3 is a diagram showing timings in writing and response to display pixels of the field sequential liquid crystal display device according to the first embodiment of the present invention. FIG. 4 is a diagram for explaining the operation of the field sequential liquid crystal display device according to the first embodiment of the present invention. Next, the operation of the field sequential liquid crystal display device 100 according to the first embodiment of the present invention will be described with reference to FIG. 1, FIG. 3, and FIG. In FIG. 3, for the sake of simplification, there are three locations (FIG. 3): the upper part of the screen (screen (upper), the middle part of the screen (middle (screen)), and the lower part of the screen ((screen (lower))) 4) only the timing in each row of the display pixels 22. In the first embodiment, the cell gap is about 3.8 μm, the refractive index anisotropy of the liquid crystal is about 0.2, and the transmittance is minimum. The voltage is set to about 6 V. The rubbing direction is parallel rubbing in which the upper and lower substrates have the same rubbing direction, and the display unit 2 has a relatively low temperature of about 600 ° C. or less. The low-temperature polysilicon TFT (Thin Film Transistor) formed is used, and the liquid crystal 224 has a normally white display that transmits light when an off-voltage is applied, and the constituent molecules are initial molecules. Is an array An OCB mode that adopts a “bend alignment” arranged in a bow shape by applying a high voltage of about 20 V from the “splay alignment” is adopted.In the first embodiment, the liquid crystal 224 is in a white display state. About 0.1 msec is required for the response when the writing of black display is performed from 1 to 2, and the response when the display of gradation other than white is performed from the white display state. The response when the white display is written from the display state requires about 1.0 msec, that is, the response when the white display is written from the black display state is the response speed of the liquid crystal 224. Is the slowest response.

  First, as shown in FIG. 1, in the drive unit 1, an analog video signal is input to the A / D converter 11, and the analog video signal is converted into an RGB digital signal. Further, a horizontal / vertical synchronization signal is input to the PLL circuit 12. In addition, RGB digital signals converted by the A / D converter 11 are stored in the memory 14 in accordance with the timing signals generated by the memory control unit 13 (signals stored in the memory 14 for each of red, green and blue signals). The

  Further, the timing control circuit 16 generates a timing signal for writing RGB video data, a timing signal for switching the order of writing video data to the display pixels 22, and a timing signal for light emission of the LED 26. Based on the timing signal for writing the RGB video data generated by the timing control circuit 16 and the timing signal for switching the order of writing the video data to the display pixels 22, the horizontal / vertical control signal and the field sequential drive are used. The control signal is supplied to the display unit 2 via the level conversion circuit 17. Accordingly, the order of writing the RGB video data and the video data to the display pixel 22 is switched.

  Further, based on the light emission timing signal of the LED 26 generated by the timing control circuit 16, one frame (one screen is displayed) as shown in FIG. 3 by a signal from the LED control circuit 18 (see FIG. 1). Field during which red image writing, red LED 26a light emission, green image writing, green LED 26b light emission, blue image writing, and blue LED 26c light emission are performed once each during Sequential drive is performed. Note that a period for displaying each image of red, green, and blue is called one subframe. The operation for one frame in the first embodiment is driven at 120 Hz (about 8.4 msec). The operation of each subframe is driven at 360 Hz (about 2.8 msec), which is three times as fast as the operation for one frame.

  Next, an operation in one subframe (red display) of the field sequential liquid crystal display device 100 in the first embodiment will be described.

  Here, in the first embodiment, as shown in FIG. 3, before writing the color corresponding to the video signal to each display pixel 22, the response of the liquid crystal 224 to all the display pixels 22 is performed simultaneously. Writes the signal for the white display with the slowest speed. Specifically, since the display unit 2 in the first embodiment is set to normally white, an off voltage of about 1.5 V to 2.5 V is simultaneously applied to all the display pixels 22 by 0.1 msec. It is applied for the period. As a result, all the display pixels 22 start a white display response in which the liquid crystal reaction speed is the lowest. Further, after writing for performing white display on all the display pixels 22 is performed for about 0.1 msec, writing of a color corresponding to the video signal is sequentially performed on each display pixel 22.

  Further, the writing of the color corresponding to the video signal to each display pixel 22 is sequentially performed from the upper part of the screen (screen (upper)) to the lower part of the screen (screen (lower)). At this time, in the display pixel 22 arranged at the upper part of the screen (see FIG. 4), first, a response to white display writing (off-voltage application) performed simultaneously is started. In this case, since the color writing period corresponding to the video signal is in the initial stage, the response to the writing of the color signal is started with almost no response to the writing of the white display. Here, in the upper part of the screen, for example, when there is a display pixel 22 in which black is displayed in advance, the response to the writing of the white display performed simultaneously is hardly performed, so the liquid crystal 224 corresponds to the black display. In this state, the color corresponding to the video signal is written. Therefore, when the color corresponding to the video signal is white, the response is performed so as to correspond to the white display from the black display. Therefore, as described above, the response speed of the liquid crystal 224 is the response time. About 1.0 msec, which is the latest period, is required. The writing period of the video signal per display pixel 224 is very short and can be ignored. As described above, in the upper part of the screen, the writing of the color corresponding to the video signal and the response of the display pixel 22 to the writing of the color are completed in a maximum period of about 1.0 msec.

  Further, in each display pixel 22 arranged in the middle part of the screen (screen (middle)) (see FIG. 4), first, a response to the simultaneous white display writing (off voltage application) is started. In this case, since the writing period of the color corresponding to the video signal is in the middle, a response to the white display writing is performed until the writing of the color corresponding to the video signal is performed. Here, for example, when there is a display pixel 22 in which black is displayed in advance in the middle of the screen, the response to the writing of white display performed simultaneously is performed halfway (about 1/2 (about 0.5 msec)). Therefore, the color corresponding to the video signal is written from the state where the liquid crystal 224 is responding to the white display with the slowest response speed. Thereby, for example, even when white writing with the slowest response speed is performed as a video signal, the response period of the liquid crystal 224 after the writing of the video signal is about ½ of the normal white response period (0. About 5 msec). The writing period of the video signal per display pixel 224 is very short and can be ignored. As described above, in the central portion of the screen, the writing of the color corresponding to the video signal and the response of the display pixel 22 to the writing of the color are completed in a period of about 0.5 msec at the maximum.

  Here, in the first embodiment, each display pixel 22 arranged in the lower part of the screen (screen (bottom)) (see FIG. 4) is written in the latter period of the color writing period corresponding to the video signal. At the time when the writing of the color corresponding to the video signal is performed, the response to the writing of the white display performed simultaneously on all the display pixels 22 is almost completed. That is, at the bottom of the screen, the response to the writing of the voltage corresponding to the video signal is started from the state in which the response to the writing of the white display performed simultaneously on all the display pixels 22 is almost completed. For example, when there is a display pixel 22 in which black is displayed in advance at the lower part of the screen, the response to the writing of the white display performed simultaneously is almost completed, so that the response speed is the slowest as the color corresponding to the video signal. Even when white writing is performed, it is substantially the same as writing from white display to white display. In addition, when the voltage corresponding to the video signal is a voltage other than the white display voltage having the slowest response speed, it is substantially the same as the writing of a color other than white from the white display. is there. As described above, in the lower part of the screen, the color writing corresponding to the video signal and the response of the display pixel 22 to the color writing are completed in a period of about 0.1 msec. Moreover, in the display pixel 22 in which the color corresponding to the video signal is finally written among all the display pixels 22, the response of the display pixel 22 is completed in a period of about 0.1 msec as described above. As a result, the response to the color writing of all the display pixels 22 is completed about 0.1 msec after the color writing to all the display pixels 22 is completed. That is, in one subframe, the writing corresponding to the video signal to all the display pixels 22 and the response to the writing are completed in a period of about 1.1 msec.

  Further, after the response to the writing corresponding to the video signal of all the display pixels 22 is completed, the red LED 26a emits light for a period of about 1.6 msec and the operation of one subframe (red display) is completed, and the green display is performed. The corresponding subframe is started, and after the subframe corresponding to the green display ends, the subframe corresponding to the blue display is started. As described above, the operation of one frame is completed once when the operations of the subframes corresponding to red, green, and blue are performed once.

  In the first embodiment, as described above, a predetermined voltage (off voltage) is applied to all the display pixels 22 all at once before sequentially writing the voltage corresponding to the video signal to each display pixel 22 in one subframe period. For example, if a voltage with the slowest response speed of the liquid crystal 224 is applied as a predetermined voltage (off voltage), all the display pixels 22 have the slowest response speed of the liquid crystal 224 at the same time. A response to a predetermined voltage is started, and a response to each video signal is sequentially started from the display pixel 22 in which a voltage corresponding to the video signal is written. Accordingly, when the voltage corresponding to the video signal is sequentially written, the display pixels 22 to which writing is performed in the second half are performed with respect to all the display pixels 22 at the time when the voltage corresponding to the video signal is written. Since the response to the application of the predetermined voltage performed simultaneously is almost completed, the response to the writing of the voltage corresponding to the video signal from the state where the response to the predetermined voltage with the slowest response speed of the liquid crystal 224 is almost completed. Can start. In this case, even if the voltage with respect to the video signal is the voltage with the slowest response speed of the liquid crystal 224, the voltage with the slowest response speed of the liquid crystal 224 has already been written and the response of the liquid crystal 224 has been completed. No response period is required. In addition, when the voltage corresponding to the video signal is a voltage other than the voltage with the slowest response speed, the response of the liquid crystal 224 is completed faster than when the liquid crystal 224 responds to the voltage with the slowest response speed. Therefore, the response time of the liquid crystal 224 can be shortened. As a result, the response period of the liquid crystal 224 after writing to the display pixel 22 where writing is performed in the latter half can be shortened, so that the lighting time of the LED 26 can be lengthened, and as a result, field sequential The display of the liquid crystal display device 100 can be brightened.

  In the first embodiment, as described above, the voltage corresponding to the video signal is sequentially written in each display pixel 22 and the LEDs 26 are turned on after a predetermined time has elapsed, whereby all the display pixels 22 are configured. After the writing of the voltage corresponding to the video signal is completed, the backlight can be turned on. Accordingly, unlike the case where light sources corresponding to RGB are emitted for each pixel region, it is possible to suppress the simultaneous emission of a plurality of light sources, and thus color mixing occurs in the pixel region where the plurality of display pixels 22 are arranged. Can be suppressed.

  In the first embodiment, as described above, after a predetermined voltage (off voltage) is applied to all the display pixels 22 at once, a voltage corresponding to the video signal is sequentially written to each display pixel 22. At this time, the display pixel 22 written in the second half is configured so that the response speed of the display pixel 22 written in the second half is faster than the response speed of the display pixel 22 written in the first half. Since the period until the response is completed is shorter than that of the written display pixel 22, the period until the entire response of the display pixel 22 after all the display pixels 22 are written is shortened accordingly. can do. Thereby, since the light emission time of LED26 can be lengthened, the display of the field sequential liquid crystal display device 100 can be made bright.

  In the first embodiment, as described above, writing is performed in the second half by configuring the voltage to be applied to all the display pixels 22 at once so that the response speed of the liquid crystal 224 is the slowest. Since the voltage at which the response speed of the liquid crystal 224 is the slowest is already written in the display pixel 22 to which writing is performed in the second half when the writing of the display pixel 22 is started, the response of the liquid crystal 224 is completed. The response period of the liquid crystal 224 after writing to the display pixel 22 in which writing is performed in the latter half can be shortened.

  In the first embodiment, as described above, the voltage applied simultaneously to all the display pixels 22 is configured to be an off voltage, so that, for example, the voltage with the slowest response speed of the liquid crystal is the off voltage. In this case, writing to the voltage with the slowest response speed of the liquid crystal can be easily performed for all the display pixels 22 by applying only the off voltage.

  In the first embodiment, as described above, the liquid crystal 224 is displayed in a normally white display that transmits light when no voltage is applied, and the constituent molecules are arranged in a bow shape while the voltage is applied. The liquid crystal 224 is normally white by configuring the voltage to be applied simultaneously to all the display pixels 22 so as to correspond to the video signal for displaying white. Since it is a display, writing that displays the white color with the slowest response speed of the liquid crystal 224 is simultaneously performed on all the display pixels 22 only by applying a voltage of about 1.5 V to 2.5 V, which is an off voltage. It can be carried out. In addition, by configuring the liquid crystal 224 so that the constituent molecules of the liquid crystal 224 are in a bend orientation after applying a voltage for phase transition of the liquid crystal, the change in the orientation of the liquid crystal molecules is accelerated by the bending of the bow. The response speed with respect to the writing of the voltage corresponding to the video signal can be increased.

  In the first embodiment, as described above, the backlight as the light source is configured by the LED 26, so that the space required for the arrangement becomes smaller than when a fluorescent lamp is used for the backlight. Therefore, the apparatus main body can be reduced in size.

  In the first embodiment, as described above, the backlight as the light source is configured by the three LEDs 26a, 26b, and 26c corresponding to RGB, and when displaying the video, the three LEDs 26a corresponding to RGB. , 26b and 26c are spatially displayed in red (R), green (G), and blue (B) by being configured to be controlled by field sequential driving that is controlled so as to light up in order for each color. In the method of obtaining a desired color by mixing, one display pixel has to be divided into three for each color, whereas in field sequential driving, one color is displayed in order because each color is turned on in turn. There is no need to divide the pixel into three. Therefore, the aperture ratio can be increased correspondingly, and the display on the display unit 2 can be brightened.

  Further, in the first embodiment, as described above, a period during which writing is performed by applying a predetermined voltage (off voltage) to all the display pixels 22 at once is performed, and a voltage corresponding to the video signal is set to each display pixel 22. Thus, even if an operation for performing writing by applying a predetermined voltage to all the display pixels 22 all at once is added, the entire operation period is longer than that of the sequential writing period. However, since the overall response period shortened due to the simultaneous writing operation is increased, the response period of the display pixels 22 can be shortened as a whole.

(Second Embodiment)
FIG. 5 is a block diagram showing an overall configuration of an impulse drive type liquid crystal display device according to a second embodiment of the present invention. FIG. 6 is a diagram showing the operation timing in one frame period of the impulse drive type liquid crystal display device according to the second embodiment of the present invention. In the second embodiment, unlike the field sequential liquid crystal display device 100 described in the first embodiment, an impulse drive type liquid crystal display device 200 will be described. Note that the impulse drive is a drive method for controlling the image not to be displayed until the image is switched to the next frame after the image is displayed in a very short period within the frame.

  As shown in FIG. 5, the impulse drive type liquid crystal display device 200 according to the second embodiment includes a backlight 41 as a light source in the display unit 20, and the drive unit 10 matches the timing of impulse drive. A backlight control circuit 40 that controls light emission of the backlight 41 and stop of the light emission is provided.

  Further, as shown in FIG. 6, unlike the first embodiment, the impulse drive type liquid crystal display device 200 according to the second embodiment simultaneously writes white display signals to all the display pixels 22 in one frame period. The combination of the operation, the color writing operation corresponding to the video signal to each display pixel 22, and the lighting operation of the backlight 41 is performed once. In the second embodiment, the cell gap is set to about 6 μm, the anisotropy of the refractive index of the liquid crystal is set to about 0.15, and the minimum transmittance voltage is set to about 6V. The rubbing direction is parallel rubbing in which the rubbing direction is the same between the upper and lower substrates. In the second embodiment, the liquid crystal 224 responds when the black display is written from the white display state, and when the display of the gradation other than white is written from the white display state. Response requires about 0.2 msec. Further, it takes about 2.0 msec for a response when white display is written from a black display state. That is, the response when the white display is written from the black display state is the response with the slowest response speed of the liquid crystal 224.

  Specifically, before writing the color corresponding to the video signal to each display pixel 22, first, an off voltage (for example, 0 V to 1.5 V) is simultaneously applied to all the display pixels 22. 1.0 msec is applied. Thereby, all the display pixels 22 start a white display response all at once. Further, after writing for white display on all the display pixels 22 is performed for about 1.0 msec, writing of the color corresponding to the video signal is performed for each display pixel 22 over about 3.0 msec. Here, in the second embodiment, out of all the display pixels 22, a period of about 0.2 msec from the writing of the color corresponding to the video signal in the display pixel 22 where the writing of the color corresponding to the video signal is performed last. To complete the response. As a result, the response of the display pixel 22 to which the color corresponding to the video signal is finally written is completed about 0.2 msec after the color writing to all the display pixels 22 is completed. That is, in one frame period, the writing corresponding to the video signal to all the display pixels 22 and the response corresponding to the writing are completed in a period of about 3.2 msec. Further, after the response to the color writing of all the display pixels 22 is completed, the backlight 41 is turned on for a period of about 4.1 msec.

  Other configurations and operations of the second embodiment are the same as those of the first embodiment.

  In the second embodiment, as described above, a predetermined voltage (off voltage) is applied to all the display pixels 22 all at once before sequentially writing the voltage corresponding to the video signal to each display pixel 22 within one frame period. For example, if the voltage with the slowest response speed of the liquid crystal 224 is applied as the predetermined voltage, the display pixel 22 in which the voltage corresponding to the video signal is written in the second half is At the time when the voltage corresponding to the video signal is written, the response to the application of the predetermined voltage performed simultaneously is close to being completed. In this case, the response time of the liquid crystal 224 can be shortened because the response of the liquid crystal 224 is completed earlier than the response to the voltage at which the response speed of the liquid crystal 224 is the slowest. Thereby, since the response period of the liquid crystal 224 after the writing to the display pixel 22 where writing is performed in the latter half can be shortened, the lighting time of the LED 26 can be lengthened, and as a result, The display of the impulse drive type liquid crystal display device 200 can be brightened.

  In the second embodiment, when the video is displayed, the backlight 41 is configured to be controlled by the impulse drive that blinks at a predetermined time interval (one frame interval), whereby the video is displayed by the impulse drive. When displayed, since the image is controlled to blink at a predetermined time interval, it is possible to suppress an afterimage from remaining on the retina. Thereby, the display performance of a moving image can be improved. The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the first embodiment, an example in which an LED (light emitting diode element) is used as a backlight light source has been described. However, the present invention is not limited to this, and a backlight light source other than an LED may be used. .

  In the first embodiment, an example of the OCB mode is shown. However, the present invention is not limited to this, and a TN (twisted nematic) mode, an ECB (electric field control birefringence) mode, a VA (vertical alignment) mode, and the like. Can be. In the second embodiment, the mode is not described. However, as in the first embodiment, the OCB mode, the TN mode, the ECB mode, the VA mode, and the like can be used.

  In the first and second embodiments, the liquid crystal is an example of a normally white display that transmits light without applying a voltage. However, the present invention is not limited to this, and no voltage is applied. The display may be a normally black display that does not transmit light. In the case of normally black, black display has the slowest response speed of liquid crystal. Therefore, before writing corresponding to the video signal to each display pixel, a signal (off voltage) for performing black display all at once. Write.

  In the first and second embodiments, the off voltage is applied to all the pixels at the same time by applying the off voltage to the display pixels to perform white display on the liquid crystal. Overall, an example in which the response time from black display to white display of the display pixel is shortened has been shown. However, the present invention is not limited to this, and as long as there is a difference in response speed between gradations, all pixels The present invention can also be applied to the case where the display pixels respond to colors other than white when off voltages are applied simultaneously.

  In the first and second embodiments, the example in which the voltage with the slowest response speed of the liquid crystal is written all at once has been shown. However, the present invention is not limited to this, and a predetermined voltage between black display and white display is set. You may make it apply. Also in this case, for example, in a normally white display, the response speed from the intermediate predetermined voltage to the white display is faster than the response speed from the black display to the white display, and thus the same effect can be obtained. Can do.

1 is a block diagram showing an overall configuration of a field sequential liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows the structure of the display pixel by 1st Embodiment of this invention. It is a figure which shows the timing in the writing to the display pixel of the field sequential liquid crystal display device by 1st Embodiment of this invention, and a response. It is a figure for demonstrating operation | movement of the field sequential liquid crystal display device by 1st Embodiment of this invention. It is a block diagram which shows the whole structure of the impulse drive type liquid crystal display device by 2nd Embodiment of this invention. It is a figure which shows the timing in the writing to the display pixel of the impulse drive type liquid crystal display device by 2nd Embodiment of this invention, and a response.

Explanation of symbols

22 Display pixel 26 (26a, 26b, 26c) LED (backlight)
100 field sequential liquid crystal display device (display device)
224 liquid crystal

Claims (10)

A plurality of display pixels including liquid crystal;
With a backlight as a light source,
Within one frame period, a predetermined voltage is applied to all the display pixels all at once, then a voltage corresponding to a video signal is sequentially written to each of the display pixels, and then the backlight is turned on after a predetermined time has elapsed. A display device configured as described above.   After applying a predetermined voltage to all the display pixels all at once, when the voltage corresponding to the video signal is sequentially written to each of the display pixels, 2. The display device according to claim 1, wherein the response speed of the display pixel written in is configured to be faster than the response speed of the display pixel written in the first half.   The display device according to claim 1, wherein the voltage applied to all the display pixels simultaneously is a voltage at which the response speed of the liquid crystal is the slowest.   The display device according to claim 1, wherein the voltage applied to all the display pixels simultaneously is an off voltage. The liquid crystal has a normally white display that transmits light with an off-voltage applied, and a bend alignment in which constituent molecules are arranged in a bow after applying a voltage that causes phase transition of the liquid crystal. Configured,
5. The display device according to claim 1, wherein the voltage applied to all the display pixels simultaneously is a voltage corresponding to a video signal for displaying white. The liquid crystal has a normally black display that does not transmit light when an off voltage is applied, and a bend alignment in which constituent molecules are arranged in a bow shape after a voltage that causes phase transition of the liquid crystal is applied. Configured,
The display device according to claim 1, wherein the voltage applied to all the display pixels at once is a voltage corresponding to a video signal for displaying black.   The display device according to claim 1, wherein the backlight includes a light emitting diode element. The backlight is composed of three light emitting diode elements corresponding to RGB,
8. When displaying an image, the three light emitting diode elements corresponding to RGB are configured to be controlled by field sequential driving that is controlled so as to be lit in order for each color. The display device according to any one of the above.   8. The display device according to claim 1, wherein when displaying an image, the backlight is controlled by impulse driving that blinks at predetermined time intervals. 9.   A period in which writing is performed by applying a predetermined voltage to all the display pixels at once is configured to be shorter than a period in which a voltage corresponding to the video signal is sequentially written in each of the display pixels. Item 10. The display device according to any one of Items 1 to 9.

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