JP2006323418A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device of field sequential system capable of improving the visibility out of doors. <P>SOLUTION: A data of a prescribed level is added to pixel data PD of each emission light color, inputted according to the display image by a pixel data conversion circuit 25, and a color display is performed by making the input of addition pixel data PD' obtained synchronized with the addition with the light emission timing of each light emission color (R, G, B) by means of a backlight 22. Color display, based on such a addition pixel data PD', is switched to the color display based on the original pixel data PD by a switching circuit 24, based on the ambient illuminance measured by an illuminance measurement part 23. Furthermore, the prescribed level to be added is selected properly, based on the ambient illuminance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a field sequential display device that performs color display by synchronizing the emission timing of each emission color and the input of pixel data corresponding to each emission color.

  With the progress of the so-called information society in recent years, electronic devices represented by personal computers, PDAs (Personal Digital Assistants) and the like have been widely used. With the spread of such electronic devices, there is a demand for portable devices that can be used both in the office and 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.

  Liquid crystal display devices are roughly classified into a reflection type and a transmission type. The reflective type is a configuration in which light incident from the front of the liquid crystal panel is reflected on the back of the liquid crystal panel and the image is visually recognized by the reflected light. The transmissive type is from a light source (backlight) provided on the back of the liquid crystal panel. In this configuration, an image is visually recognized with transmitted light. Since the reflective type does not have a constant amount of reflected light depending on environmental conditions and is inferior in visibility, in particular, as a display device such as a personal computer for performing multi-color or full-color display, a transmissive color liquid crystal using a color filter is generally used. A display device is in use.

  Currently, color liquid crystal display devices of a TN (Twisted Nematic) type using a switching element such as a TFT (Thin Film Transistor) are widely used. This TFT-driven TN type liquid crystal display device has a higher display quality than an STN (Super Twisted Nematic) type, but the light transmittance of the liquid crystal panel is currently only about 4%, so that a high screen brightness can be obtained. Requires a high-brightness backlight. For this reason, the power consumption by a backlight will become large. In addition, since color display using a color filter is used, one pixel must be composed of three sub-pixels, and it is difficult to achieve high definition, and the display color purity is not sufficient.

  In order to solve such a problem, the present inventors use a ferroelectric liquid crystal element or an antiferroelectric liquid crystal element with a high response speed to an applied electric field as a liquid crystal element, and time-divides the same pixel with three primary colors. We are developing a field-sequential liquid crystal display device that performs color display by emitting light.

Such a liquid crystal display device includes a liquid crystal panel using a ferroelectric liquid crystal element or anti-ferroelectric liquid crystal element capable of a high-speed response on the order of several hundreds to several microseconds, and red, green, and blue light in a time-sharing manner. A color display is realized by combining a backlight capable of emitting light and synchronizing the switching of the liquid crystal element and the light emission of the backlight.
JP 2000-111866 A Japanese Patent Laid-Open No. 11-98521 Japanese Patent Laid-Open No. 2002-116736 JP 2001-281624 A JP 2002-62850 A Japanese Patent Laid-Open No. 3-18823 JP-A-7-281647 JP 2001-109434 A JP 2000-19488 A JP-A-6-161377

  The field-sequential display device as described above does not require sub-pixels as compared with the color filter-type display device, so that display with higher definition can be easily performed and a color filter is used. Therefore, the light emission of the light source is used as it is for display, and thus has advantages such as high brightness, excellent display color purity, high light utilization efficiency, and low power consumption.

  However, field-sequential display devices are difficult to apply as reflective / semi-transmissive types like color filter-type display devices, and when used in portable devices that are supposed to be used indoors or outdoors. There is a problem with the visibility in the outdoors.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a field sequential display device capable of improving outdoor visibility.

  The display device according to the first aspect of the present invention performs color display by switching a plurality of emission colors of the light source over time and synchronizing the emission timing of each emission color and the input of pixel data of each emission color according to the display image. In the field sequential display device, an addition means for obtaining addition pixel data by adding addition data to pixel data of each light emission color inputted according to a display image, and the addition pixel data is inputted from the addition means, A means for performing color display by synchronizing the light emission timing of each light emission color and the input of the added pixel data, a case of performing color display based on the pixel data input in accordance with a display image, and the adding means Switching means for switching between color display and color display based on the added pixel data obtained in this manner.

  In the first invention, data of a predetermined level is added to pixel data of each light emission color input according to the display image, and addition pixel data obtained by adding the data and each light emission color (R, G, Color display is performed in synchronization with the light emission timing of B). By adding data of a predetermined level to the pixel data of each emission color in order to increase the screen brightness, visibility is enhanced even in an environment with high illuminance such as outdoors. In this case, the sub-frames are the same as the three colors R, G, and B. For example, there is no need to change to a sub-frame such as R, G, B, and W (white), no change in the driving sequence, The visibility can be easily improved only by changing the pixel data for use. In addition, color display based on added pixel data obtained by adding predetermined level data to pixel data of each emission color input according to the display image, and pixel data of each emission color input according to the display image Switch between color display based on. Therefore, pixel data can be converted only when visibility needs to be improved, and when sufficient visibility is obtained, display with high color purity can be performed.

  A display device according to a second invention is characterized in that, in the first invention, the display device comprises a measuring means for measuring ambient illuminance and a means for controlling switching at the switching means based on a measurement result of the measuring means. To do.

  In the second invention, the switching in the first invention is performed based on the ambient illuminance. Therefore, it is possible to easily achieve a balance between visibility improvement and display color purity as required.

  According to a third aspect of the present invention, there is provided a display device according to the first or second aspect, wherein the storage means stores a plurality of types of data having different levels used as the addition data, and the plurality of types stored in the storage means. Selecting means for selecting one type of data from the data.

  In the third aspect of the invention, there are a plurality of levels of data to be added to the pixel data of each light emission color input according to the display image, and one level of data among them is stored. Select and add to the input pixel data of each emission color. Therefore, the level of data to be added can be selected as appropriate, and the balance between improved visibility and display color purity can be easily achieved.

  A display device according to a fourth invention is characterized in that, in the third invention, the display device comprises a measuring means for measuring ambient illuminance and a means for controlling selection by the selecting means based on a measurement result of the measuring means. To do.

  In the fourth invention, the level of data to be added in the third invention is selected based on the ambient illuminance. Therefore, it is possible to easily achieve a balance between visibility improvement and display color purity as required.

  The display device according to a fifth aspect of the invention is characterized in that, in the first to fourth aspects of the invention, the added data is achromatic white data.

  In the fifth aspect of the invention, the data added to the pixel data of each emission color input according to the display image is achromatic white data. Therefore, a significant change in display color can also be suppressed by this data addition.

  A display device according to a sixth invention is characterized in that, in the first to fifth inventions, the display device comprises means for controlling the intensity of a plurality of emission colors of the light source.

  In the sixth aspect of the invention, by increasing the intensity of the plurality of emission colors as necessary, it is possible to improve the luminance during white display, and the visibility can be further improved.

  According to a seventh aspect of the present invention, in the first to sixth aspects of the invention, the display device further comprises means for detecting whether or not the level of the input pixel data is equal to or lower than a predetermined level, and the level of the input pixel data is When the level is lower than the predetermined level, the addition means does not add the addition data.

  In the seventh aspect of the invention, when the level of the pixel data input according to the display image is equal to or lower than the predetermined level, for example, when the pixel data is black, data addition is not performed. Therefore, it is possible to improve visibility while maintaining a display with high white / black contrast.

  In the present invention, a predetermined level of data is added to the pixel data of each light emission color input according to the display image, and the input pixel data obtained by the addition is synchronized with the light emission timing of each light emission color. Since the display is performed, the screen luminance can be increased, and the visibility can be increased even in an environment with high illuminance such as outdoors without changing the drive sequence.

  In addition, color display based on added pixel data obtained by adding predetermined level data to pixel data of each emission color input according to the display image, and pixel data of each emission color input according to the display image Since the color display based on is switched, the pixel data can be converted only when the visibility needs to be improved, and when sufficient visibility is obtained, the display with high color purity is performed. be able to. Since this switching is performed based on ambient illuminance, it is possible to easily achieve a balance between visibility improvement and display color purity as required.

  In addition, there are a plurality of levels of data to be added to the pixel data of each emission color input according to the display image, and data of one type among them is selected and input. Therefore, the level of the data to be added can be selected as appropriate, and the balance between the improvement of the visibility and the display color purity can be easily achieved. Since this selection is performed based on the ambient illuminance, it is possible to easily achieve a balance between visibility improvement and display color purity as required.

  In addition, since the data added to the pixel data of each luminescent color input in accordance with the display image is achromatic white data, a significant change in display color can be suppressed by this data addition.

  In addition, since the intensity of the plurality of emission colors is increased as necessary, it is possible to improve the luminance during white display and further improve the visibility.

  In addition, when the level of pixel data input according to the display image is below a predetermined level, data addition is not performed, so that a display with high white / black contrast is maintained and visibility is improved. Can be achieved.

  Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. Note that the present invention is not limited to the following embodiments.

  FIG. 1 is a block diagram showing a circuit configuration of a liquid crystal display device of the present invention, FIG. 2 is a schematic sectional view of the liquid crystal panel and a backlight, FIG. 3 is a schematic diagram showing an example of the overall configuration of the liquid crystal display device, FIG. 4 is a diagram illustrating a configuration example of an LED array that is a light source of a backlight.

  In FIG. 1, reference numerals 21 and 22 denote a 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. .. Are formed in this order, and 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.

  Between the common electrode 3 and the pixel electrodes 40, 40..., A driving unit 50 including a data driver 32 and a scan driver 33 described later is connected. The data driver 32 is connected to a TFT (Thin Film Transistor) 41 via a signal line 42, and the scan driver 33 is connected to the TFT 41 via a scanning line 43. The TFT 41 is on / off controlled by the data driver 32 and the scan driver 33. The individual pixel electrodes 40, 40... Are connected to the TFT 41. Therefore, the transmitted light intensity of each pixel is controlled by a signal from the data driver 32 given via the signal line 42 and the TFT 41.

  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. A 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. As shown in FIG. 4, the LED array 7 emits light of three primary colors, that is, red (R), green (G), and blue (B) on the surface facing the light guide and light diffusion plate 6. The LEDs are arranged sequentially and repeatedly. Then, red, green, and blue LEDs are caused to emit light in the red, green, and blue subframes, respectively. 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.

  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 color of the backlight 22 are controlled in synchronization with the data write / erase scan of the liquid crystal panel 21.

  In FIG. 1, reference numeral 23 denotes an illuminance measurement unit that measures brightness outside the liquid crystal display device (illuminance near the display unit). The illuminance measurement unit 23 outputs the measurement result of illuminance to the switching circuit 24 and the pixel data conversion circuit 25. To do. The switching circuit 24 is set to receive display pixel data PD from an external personal computer, for example, and perform data addition (data addition processing to the pixel data PD as described later), which is a feature of the present invention. If it is, the input pixel data PD is output to the pixel data conversion circuit 25. If the data addition is not set, the input pixel data PD is output to the image memory unit 30 as it is. Switching whether or not this data addition is performed is controlled based on the measurement result of the illuminance from the illuminance measurement unit 23.

  The pixel data conversion circuit 25 adds predetermined level data to the pixel data PD for each of the input red, green, and blue colors according to various methods to be described later, and converts the data to pixel data PD ′ (added pixel data). The converted pixel data PD ′ is output to the image memory unit 30. Specifically, the pixel data conversion circuit 25 selects and inputs one type of addition data from the data storage unit 26 that stores a plurality of types of data having different levels (number of gradations) used as data to be added. Pixel data PD ′ is obtained by adding the selected addition data to the pixel data PD to be obtained, and the obtained pixel data PD ′ is output to the image memory unit 30. Which level (the number of gradations) of addition data is selected is controlled based on the illuminance measurement result from the illuminance conversion unit 25.

  Reference numeral 31 denotes a control signal generation circuit that receives a synchronization signal SYN from a personal computer and generates a control signal CS and a data inversion control signal DCS. Pixel data PD or PD ′ is output from the image memory unit 30, and a data inversion control signal DCS is output from the control signal generation circuit 31 to the data inversion circuit 36. The data inversion circuit 36 generates inverse pixel data obtained by inverting the input pixel data PD or PD ′ according to the data inversion control signal DCS, and the pixel data PD or PD ′ is supplied to the liquid crystal panel via the data driver 32. A voltage having a polarity and a substantially equal magnitude is applied.

  A control signal CS is output from the control signal generation circuit 31 to the reference voltage generation circuit 34, the data driver 32, the scan driver 33, and the backlight control circuit 35, respectively. The reference voltage generation circuit 34 generates 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 outputs a signal to the signal line 42 of the pixel electrode 40 based on pixel data or reverse pixel data received from the image memory unit 30 via the data inversion circuit 36. In synchronization with the output of this signal, the scan driver 33 sequentially scans the scanning lines 43 of the pixel electrodes 40 line by line. The backlight control circuit 35 applies drive voltage to the backlight 22 and causes the LEDs of the red, green, and blue colors included in the LED array 7 of the backlight 22 to emit light in a time-sharing manner.

  Next, the operation of the liquid crystal display device according to the present invention will be described. Display pixel data PD is input from the personal computer to the switching circuit 24. Based on the measurement result of the illuminance measurement unit 23, when the ambient illuminance is lower than a predetermined value, the pixel data PD input to the switching circuit 24 is sent to the image memory unit 30. On the other hand, when the surrounding illuminance is higher than a predetermined value, the pixel data PD input to the switching circuit 24 is sent to the pixel data conversion circuit 25 and data addition is performed.

  That is, the pixel data conversion circuit 25 adds data of a predetermined level (for gradations) selected based on the ambient illuminance to the input pixel data PD, and the addition adds pixel data PD ′. Is obtained. This pixel data PD ′ is sent to the image memory unit 30. However, when the input pixel data is black, the pixel data conversion circuit 25 does not add data. The specific contents of this data addition process will be described in detail later.

  The image memory unit 30 temporarily stores the pixel data PD or PD ′, and then outputs the pixel data PD or PD ′ when receiving the control signal CS output from the control signal generation circuit 31. When the pixel data PD or PD ′ is supplied to the image memory unit 30, the synchronization signal SYN is supplied to the control signal generation circuit 31, and the control signal generation circuit 31 receives the control signal CS and the data inversion when the synchronization signal SYN is input. A control signal DCS is generated and output. The pixel data PD or PD ′ output from the image memory unit 30 is given to the data inversion circuit 36.

  The data inversion circuit 36 passes the pixel data PD or PD ′ as it is when the data inversion control signal DCS output from the control signal generation circuit 31 is at L level, while the data inversion control signal DCS passes through it when the data inversion control signal DCS is at H level. Inverse pixel data is generated and output. Therefore, the control signal generation circuit 31 sets the data inversion control signal DCS to the L level during the data write scan, and sets the data inversion control signal DCS to the H level during the data erase scan.

  The control signal CS generated by the control signal generation circuit 31 is supplied to the data driver 32, the scan driver 33, the reference voltage generation circuit 34, and the backlight control circuit 35. When receiving the control signal CS, the reference voltage generation circuit 34 generates 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.

  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 or the inverse pixel data output from the image memory unit 30 via the data inversion circuit 36. Is output. When receiving the control signal CS, the scan driver 33 sequentially scans the scanning lines 43 of the pixel electrodes 40 line by line. The TFT 41 is driven in accordance with the output of the signal from the data driver 32 and the scan of the scan driver 33, and a voltage is applied to the pixel electrode 40 to control the transmitted light intensity of the pixel.

  When receiving the control signal CS, the backlight control circuit 35 applies a drive voltage to the backlight 22 to time-divide the red, green, and blue LEDs of the LED array 7 of the backlight 22. Light is emitted, and red light, green light, and blue light are sequentially emitted over time.

  FIG. 5 is a time chart showing display control in the liquid crystal display device of the present invention. FIG. 5 (a) shows the light emission timings of red, green and blue colors of the backlight 22 (LED), and FIG. 5 (b) shows the liquid crystal. The scanning timing of each line of the panel, FIG. 5C shows the color development state of the liquid crystal panel. One frame is divided into three subframes. As shown in FIG. 5A, red in the first subframe, green in the second subframe, and blue in the third subframe, respectively. Make it emit light.

  On the other hand, as shown in FIG. 5B, the liquid crystal panel 21 is scanned twice during the sub-frames of red, green, and blue. 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 is supplied to each pixel of the liquid crystal panel 21 to adjust the transmittance. This enables full color display. In the data erasing scan, a voltage having the same magnitude as that in the data writing scan and a reverse polarity is supplied to each pixel of the liquid crystal panel, and the display of each pixel of the liquid crystal panel 21 becomes substantially black, and further to the liquid crystal. Is prevented from being applied.

  Here, in the present invention, the data for the selected number of gradations is added to the original pixel data of the three colors red, green, and blue, if necessary, so that three colors of red, green, and blue are added. The pixel data is converted into color addition pixel data, and a voltage corresponding to the addition pixel data is supplied. Various methods as described below are possible for such data addition processing.

(First embodiment)
After the TFT substrate having the pixel electrodes 40, 40... (A matrix diagonal of 3.2 inches having a pixel number of 640 × 480) and the glass substrate 2 having the common electrode 3 are washed, polyimide is applied at 200 ° C. By baking for 1 hour, a polyimide film of about 200 mm was formed as the alignment films 11 and 12. Further, these alignment films 11 and 12 are rubbed with a cloth made of rayon, these two substrates are overlapped so that the rubbing directions are parallel, and a spacer made of silica having an average particle diameter of 1.4 μm between them. A blank panel was produced by superposing the gaps at 14 while maintaining the gap. A ferroelectric liquid crystal material having a spontaneous polarization magnitude of 10 nC / cm ² was sealed between the alignment films 11 and 12 of this empty panel to form a liquid crystal layer 13. The encapsulated ferroelectric liquid crystal material exhibits monostable characteristics, and the maximum tilt angle when a voltage of the first polarity is applied is 53 °, and the second polarity is opposite to the first polarity. The maximum tilt angle when a voltage was applied was 5 °. The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state to form a liquid crystal panel 21, and the average molecular axis of the liquid crystal molecular director when no voltage is applied and the polarizing axis of one polarizing film are substantially matched. It was in a dark state.

  The liquid crystal panel 21 thus manufactured and the backlight 22 using the LED array 7 capable of switching monochromatic surface emission of red, green, and blue as a light source are superposed, and field sequential is performed according to the driving sequence shown in FIG. Color display by the method was performed.

  As shown in FIG. 6, the color display is based on color display using addition pixel data obtained by adding data for a predetermined gradation to pixel data input according to a display image, and pixel data input according to the display image. The color display was performed while switching based on the measurement result of the surrounding illuminance in the illuminance measuring unit 23. In this example, the input pixel data (FIG. 6A) is added with data for 50 gradations corresponding to 255 gradations for each of R (red), G (green), and B (blue) (FIG. 6 (FIG. 6 (a)). b)).

  First, when display is performed indoors with an illuminance of 700 lux, display is performed according to the added pixel data obtained by adding data for 50 gradations to the pixel data input according to the display image, and input according to the display image. High visibility was achieved both in the display using pixel data. However, the display color purity was higher in the latter display than in the former display.

  Next, when the display is performed outdoors with an illuminance of 15000 lux, the display based on the added pixel data obtained by adding the data for 50 gradations to the pixel data input according to the display image depends on the display image. Compared with the display by the input pixel data, high visibility could be obtained. In the latter display, only a display with low visibility could be performed.

(Second Embodiment)
As in the first embodiment, after the TFT substrate having the pixel electrodes 40, 40... (Matrix-shaped diagonal 3.2 inches having 640 × 480 pixels) and the glass substrate 2 having the common electrode 3 are cleaned. The polyimide was applied and baked at 200 ° C. for 1 hour to form about 200 mm of polyimide films as the alignment films 11 and 12. Further, these alignment films 11 and 12 are rubbed with a cloth made of rayon, these two substrates are overlapped so that the rubbing directions are parallel, and a spacer made of silica having an average particle diameter of 1.4 μm is placed between them. A blank panel was produced by superposing the gaps at 14 while maintaining the gap. A ferroelectric liquid crystal material exhibiting a bistable characteristic having a spontaneous polarization of 8 nC / cm ² was sealed between the alignment films 11 and 12 of the empty panel to form a liquid crystal layer 13. The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state to form a liquid crystal panel 21, and an average molecular axis of a liquid crystal molecular director and a polarizing axis of one polarizing film when a voltage of one polarity is applied. Were substantially matched to obtain a dark state.

  The liquid crystal panel 21 thus manufactured and the backlight 22 using the LED array 7 capable of switching monochromatic surface emission of red, green, and blue as a light source are superposed, and field sequential is performed according to the driving sequence shown in FIG. Color display by the method was performed.

  Then, color display was performed by the addition pixel data obtained by adding data for a predetermined gradation to the pixel data input according to the display image. In this example, the input pixel data includes 50 gradations, 75 gradations, and 100 gradations with respect to 255 gradations of R (red), G (green), and B (blue), respectively. The data was added.

  First, when the visibility is evaluated by visual display outdoors with an illuminance of 15000 lux, when 75 gradations of data are added to each of R (red), G (green), and B (blue) Was the easiest to see. Next, when the visibility was evaluated by visual display outdoors with an illuminance of 20000 lux, data for 100 gradations was added to each of R (red), G (green), and B (blue). Time was the easiest to see.

  Therefore, from the above result, the data for the optimum gradation to be added is selected based on the measurement result of the surrounding illuminance in the illuminance measurement unit 23, and this selected floor is selected as the pixel data input according to the display image. It can be seen that the visibility can be improved by performing color display using the added pixel data obtained by adding the data of the adjustments.

(Third embodiment)
As in the first embodiment, after the TFT substrate having the pixel electrodes 40, 40... (Matrix-shaped diagonal 3.2 inches having 640 × 480 pixels) and the glass substrate 2 having the common electrode 3 are cleaned. The polyimide was applied and baked at 200 ° C. for 1 hour to form about 200 mm of polyimide films as the alignment films 11 and 12. Further, these alignment films 11 and 12 are rubbed with a cloth made of rayon, these two substrates are overlapped so that the rubbing directions are parallel, and a spacer made of silica having an average particle diameter of 1.4 μm between them. A blank panel was produced by superposing the gaps at 14 while maintaining the gap. A ferroelectric liquid crystal material exhibiting a bistable characteristic having a spontaneous polarization of 15 nC / cm ² was sealed between the alignment films 11 and 12 of the empty panel to form a liquid crystal layer 13. The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state to form a liquid crystal panel 21, and an average molecular axis of a liquid crystal molecular director and a polarizing axis of one polarizing film when a voltage of one polarity is applied. Were substantially matched to obtain a dark state.

  The liquid crystal panel 21 thus manufactured and the backlight 22 using the LED array 7 capable of switching monochromatic surface emission of red, green, and blue as a light source are superposed, and field sequential is performed according to the driving sequence shown in FIG. Color display by the method was performed.

  Then, by adding pixel data obtained by adding data of 50 gradations to 255 gradations of R (red), G (green), and B (blue), respectively, to pixel data input according to the display image, Color display was performed. In addition, the brightness of the backlight 22 was temporarily doubled.

  As a result of investigating the display characteristics outdoors with an illuminance of 20000 lux, both visibility and display color purity are superior to the display using the added pixel data obtained by adding data for 100 gradations in the second embodiment. It was.

(Fourth embodiment)
As in the first embodiment, after the TFT substrate having the pixel electrodes 40, 40... (Matrix-shaped diagonal 3.2 inches having 640 × 480 pixels) and the glass substrate 2 having the common electrode 3 are cleaned. The polyimide was applied and baked at 200 ° C. for 1 hour to form about 200 mm of polyimide films as the alignment films 11 and 12. Further, these alignment films 11 and 12 are rubbed with a cloth made of rayon, these two substrates are overlapped so that the rubbing directions are parallel, and a spacer made of silica having an average particle diameter of 1.4 μm is placed between them. A blank panel was produced by superposing the gaps at 14 while maintaining the gap. A ferroelectric liquid crystal material having a spontaneous polarization of 15 nC / cm ² was sealed between the alignment films 11 and 12 of the empty panel to form a liquid crystal layer 13. The encapsulated ferroelectric liquid crystal material exhibits monostable characteristics, and the maximum tilt angle when a voltage of the first polarity is applied is 58 °, and the second polarity is opposite to the first polarity. The maximum tilt angle when a voltage was applied was 5 °. The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state to form a liquid crystal panel 21, and the average molecular axis of the liquid crystal molecular director when no voltage is applied and the polarizing axis of one polarizing film are substantially matched. It was in a dark state.

  The liquid crystal panel 21 thus manufactured and the backlight 22 using the LED array 7 capable of switching monochromatic surface emission of red, green, and blue as a light source are superposed, and field sequential is performed according to the driving sequence shown in FIG. Color display by the method was performed.

  As in the first embodiment, the color display is input according to the color display based on the added pixel data obtained by adding data for a predetermined gradation to the pixel data input according to the display image and the display image. Color display based on pixel data is performed while switching based on the measurement result of ambient illuminance in the illuminance measurement unit 23, and data to be added is 255 for R (red), G (green), and B (blue), respectively. Data for 50 gradations was used. However, in this example, as shown in FIG. 7, before adding the data for 50 gradations, the pixel data (FIG. 7A) input according to the display image is multiplied by 205/255 ( In FIG. 7B, color display was performed using added pixel data (FIG. 7C) obtained by adding data for 50 gradations to the multiplication result. In this example, even if data for 50 gradations are added, the pixel data after the addition does not exceed the maximum number of gradations (255 gradations), and the whitening of the display can be prevented.

  First, when display is performed indoors with an illuminance of 700 lux, display is performed with added pixel data obtained by multiplying pixel data input according to the display image by 205/255 and adding 50 gradations of data, and display High visibility was realized both in the display using pixel data input according to the image. Further, in the former display, since the whitening of the display is eliminated, the display characteristics are better than in the case of the first embodiment.

  Next, when the display is performed outdoors with an illuminance of 15000 lux, the display is based on the added pixel data obtained by multiplying the pixel data input according to the display image by 205/255 and adding the data for 50 gradations. However, high visibility was able to be obtained compared with the display by the pixel data input according to a display image.

(Fifth embodiment)
As in the first embodiment, after the TFT substrate having the pixel electrodes 40, 40... (Matrix-shaped diagonal 3.2 inches having 640 × 480 pixels) and the glass substrate 2 having the common electrode 3 are cleaned. The polyimide was applied and baked at 200 ° C. for 1 hour to form about 200 mm of polyimide films as the alignment films 11 and 12. Further, these alignment films 11 and 12 are rubbed with a cloth made of rayon, these two substrates are overlapped so that the rubbing directions are parallel, and a spacer made of silica having an average particle diameter of 1.4 μm between them. A blank panel was produced by superposing the gaps at 14 while maintaining the gap. A bistable ferroelectric liquid crystal material having a spontaneous polarization of 15 nC / cm ² was sealed between the alignment films 11 and 12 of the empty panel to form a liquid crystal layer 13. The produced panel is sandwiched between two polarizing films 1 and 5 in a crossed Nicol state to form a liquid crystal panel 21, and an average molecular axis of a liquid crystal molecular director and a polarizing axis of one polarizing film when a voltage of one polarity is applied. Were substantially matched to obtain a dark state.

  The liquid crystal panel 21 thus manufactured and the backlight 22 using the LED array 7 capable of switching monochromatic surface emission of red, green, and blue as a light source are superposed, and field sequential is performed according to the driving sequence shown in FIG. Color display by the method was performed.

  8 and 9 are diagrams showing an example of pixel data conversion in the fifth embodiment. It is determined whether or not the input pixel data is in black display. If the input pixel data is in black display, data addition is not performed, and if the display is other than black, data addition is performed. Two methods were used for this data addition.

  In the example shown in FIG. 8, as in the first embodiment, R (red), G ( Color display was performed using added pixel data (FIG. 8B) obtained by adding data for 50 gradations to 255 gradations for green and B (blue). On the other hand, in the example shown in FIG. 9, similarly to the fourth embodiment, before adding the data for 50 gradations, pixel data including black display input according to the display image (FIG. 9A). ) Is multiplied by 205/255 (FIG. 9B), and color display is performed using added pixel data (FIG. 9C) obtained by adding data for 50 gradations to the multiplication result other than black display.

  When the display is performed outdoors with an illuminance of 15000 lux, no data is added when the display is black, and 50 gradations are added to the pixel data input according to the display image when the display is other than black. When the display is based on the added pixel data and when the display is black, no data is added. When the display is other than black, the pixel data input according to the display image is multiplied by 205/255 to obtain data for 50 gradations. High visibility can be realized both in the display by the added pixel data obtained by adding. Moreover, those displays had higher visibility than the displays in the first to fourth embodiments in which the presence / absence of data addition was not controlled depending on whether or not the data pixel was a black display.

  In the fifth embodiment described above, data addition is not performed only in the case of black display. However, not only black display but also display with a predetermined number of gradations (predetermined level) or less is detected and detected. Even if data addition is not performed on the displayed pixel data, the same effect can be obtained. In such a case, the predetermined number of gradations (predetermined level) for determining the presence or absence of data addition may be appropriately selected according to environmental conditions such as ambient illuminance.

  In the above-described example, a ferroelectric liquid crystal material is used as the liquid crystal material. However, even in a liquid crystal display device using an antiferroelectric liquid crystal material having a spontaneous polarization or a nematic liquid crystal, a field sequential method is used. Of course, the present invention can be similarly applied to color display.

  Furthermore, although the liquid crystal display device has been described as an example, the present invention can be applied to other display devices such as a digital micromirror device (DMD) as long as the display device performs color display by a field sequential method. Of course, the invention is equally applicable.

It is a block diagram which shows the circuit structure of the liquid crystal display device of this invention. It is typical sectional drawing of a liquid crystal panel and a backlight. It is a schematic diagram which shows the structural example of the whole liquid crystal display device. It is a figure which shows the structural example of a LED array. It is a time chart which shows the display control in the liquid crystal display device of this invention. It is a figure which shows an example (1st-3rd embodiment) of pixel data conversion in this invention. It is a figure which shows the other example (4th Embodiment) of pixel data conversion in this invention. It is a figure which shows the further another example (5th Embodiment) of the pixel data conversion in this invention. It is a figure which shows the further another example (5th Embodiment) of the pixel data conversion in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Common electrode 7 LED array 21 Liquid crystal panel 22 Backlight 23 Illuminance measurement part 24 Switching circuit 25 Pixel data conversion circuit 26 Data storage part 31 Control signal generation circuit 35 Backlight control circuit

Claims (7)

  In a field sequential display device that switches a plurality of emission colors of a light source over time and performs color display by synchronizing the emission timing of each emission color and the input of pixel data of each emission color according to the display image, Addition means for obtaining addition pixel data by adding addition data to pixel data of each emission color inputted according to the display image, and the addition pixel data is inputted from the addition means, and the emission timing and addition of each emission color Means for performing color display in synchronization with the input of pixel data, a case of performing color display based on the pixel data input in accordance with a display image, and based on the addition pixel data obtained by the addition means And a switching means for switching between color display and color display.   The display device according to claim 1, further comprising: a measurement unit that measures ambient illuminance; and a unit that controls switching by the switching unit based on a measurement result of the measurement unit.   2. A storage unit that stores a plurality of types of data having different levels used as the addition data, and a selection unit that selects one type of data from the plurality of types of data stored in the storage unit. Or the display apparatus of 2.   The display device according to claim 3, further comprising: a measurement unit that measures ambient illuminance; and a unit that controls selection by the selection unit based on a measurement result of the measurement unit.   The display device according to claim 1, wherein the addition data is achromatic white data.   The display device according to claim 1, comprising means for controlling the intensity of a plurality of emission colors of the light source.   A means for detecting whether or not the level of the input pixel data is equal to or lower than a predetermined level; and when the level of the input pixel data is equal to or lower than the predetermined level, the addition is performed by the adding means The display device according to claim 1, wherein addition of data is not performed.

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