JP2001091922A - Color liquid crystal display device of rgb field sequential display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color liquid crystal display device of an RGB field sequential display system capable of displaying a color image having no burning while securing high speed responsiveness. SOLUTION: This liquid crystal display element is provided with liquid crystal having spontaneous polarization to display a multilevel image. A liquid crystal driving part separates the video signal of each field into video signals for red, green and blue. A row driver and a column driver at first turn all TFTs ON and applies a triangular wavelike AC voltage on all pixels to eliminate the burning of display generated in previous subfields in respective subfields in order to sequentially display videos of R, G, B in three subfields. Next, the drivers turn the TFTs ON in a row unit to write a multilevel signal corresponding to video signal of R, G or B in the pixels. After the writing is completed, this device colors the multilevel image by projecting light of colors corresponding to the displaying multilevel image of the liquid crystal display element on the liquid crystal display element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RGB field sequential display type liquid crystal display device, and more particularly, to an RGB field sequential display type liquid crystal display device using a liquid crystal having spontaneous polarization which can operate at high speed and has less display sticking. .

[0002]

2. Description of the Related Art A color liquid crystal display device has R (red), G
Equipped with three primary color filters of (green) and B (blue), one pixel is formed by three dots, and a plurality of colors are displayed by controlling the transmittance of these three primary color dots. This color liquid crystal display element uses a three primary color filter to display one color with three dots. For this reason,
There is light absorption by the filter, and furthermore, only the transmitted light of 1/3 of the incident light is used, so the display is dark,
It is difficult to display a high-quality color image with a low resolution.

[0003] To solve these drawbacks, to make the display brighter,
As a technique for increasing the resolution, a color liquid crystal display device of an RGB field sequential display method (three primary color sequential display method) has attracted attention. A color liquid crystal display device of this type includes a liquid crystal display element for displaying black and white gradations, and R,
A color image is obtained by turning on the fluorescent lamps in synchronization with the image display of the liquid crystal display device and irradiating the light to the liquid crystal display device. is there.

According to this method, each pixel of the liquid crystal display element corresponds to a color pixel on a one-to-one basis. Therefore, the apparent number of pixels and the aperture ratio can be tripled as compared with a color filter type liquid crystal display element in which a set of three pixels corresponds to one color pixel, and a bright, high-resolution A color image can be displayed.

[0005]

The liquid crystal display device of the RGB field sequential display system must display three achromatic images of R, G, B in order to display one color image. Therefore, assuming that the frame frequency is the same, each field period of the liquid crystal display device of the RGB field sequential display method is shorter than the field period of the liquid crystal display device of the color filter method. Therefore, the liquid crystal must be driven at a high speed.

As described above, high-speed response is required for the liquid crystal of the liquid crystal display device of the RGB field sequential display system. However, in the conventional TN type liquid crystal display device using a nematic liquid crystal, the response of the liquid crystal is low, and the frame frequency cannot be increased. Therefore, satisfactory display could not be performed with the conventional liquid crystal display device.

As means for ensuring high-speed response,
It has been proposed to use a ferroelectric liquid crystal having a spontaneous polarization or an antiferroelectric liquid crystal for a liquid crystal display element.

However, in a liquid crystal display device using a ferroelectric liquid crystal or the like, since electric charges are biased due to polarization of the liquid crystal, impurity ions in the liquid crystal accumulate near the substrate and are adsorbed on the inner surface of the substrate to generate an electric field. There is a problem that the electric field causes the liquid crystal molecules to be oriented, causing display burn-in. When display burn-in occurs, for example, the display written in the R subframe remains in the next G subframe, or after displaying a still image, the previous still image remains even if the next display is rewritten. As a result, there is a problem that image quality is reduced.

For example, as shown in FIG. 8A, after drawing a white square in the center of a black background, even if the electric field is cut off, as shown in FIG. The pattern of the opposite shade is burned. Then, FIG.
As shown in (1), a phenomenon in which the previous display pattern remains even when the next depiction is performed is observed.

The present invention has been made in view of the above situation, and provides a color liquid crystal display device of an RGB field sequential display system capable of displaying a clear color image without burning while ensuring high-speed response of liquid crystal. The purpose is to:

[0011]

In order to achieve the above object, a color liquid crystal display device of an RGB field sequential display system according to a first aspect of the present invention comprises an electrode for forming a plurality of pixels arranged in a matrix. A liquid crystal display device that sandwiches a liquid crystal having spontaneous polarization and displays an image by the plurality of pixels, and is connected to the liquid crystal display device. G
(R), (G), and (B) images separated into respective colors of B (blue) are sequentially displayed in three consecutive subfields, and the R, G, and B images are displayed. A driving circuit for providing a period in which a triangular wave AC voltage is applied to an electrode of each pixel in at least one of the fields, a driving circuit for displaying one color pixel by the three sub-fields, and one surface of the liquid crystal display element And displays the R, G, and B images of the liquid crystal display element.
And a light source for sequentially irradiating R, G, and B light to the liquid crystal display element in correspondence with one subfield.

According to this configuration, since the liquid crystal display device uses liquid crystal having spontaneous polarization, high-speed response can be improved, and three frames (R subfield and G subfield) can be used as one display frame. Despite the RGB field sequential display method that requires a field and a B subfield, a high frame frequency can be secured and a high-quality image with less flicker can be displayed. In addition, a period in which a triangular-wave AC voltage is applied to each pixel is provided. With this AC voltage, display burn-in due to ion bias can be eliminated, and a clear image can be displayed.

Further, the RG according to the first aspect of the present invention
A B-field sequential display type color liquid crystal display device includes means for applying a triangular wave AC voltage to the liquid crystal of a plurality of pixels arranged in a matrix of liquid crystal display elements at once or for each row, and a matrix of liquid crystal display elements. Means for writing a gradation signal to the plurality of arranged pixels row by row.

It is desirable to apply an AC voltage to each pixel during the non-lighting period of the light source.

Furthermore, a triangular wave application period may be provided in all subfields, or a triangular wave application period may be provided in any of the three subfields of RGB.

A color liquid crystal display device of an RGB field sequential display system according to a second aspect of the present invention uses a liquid crystal having spontaneous polarization, and a liquid crystal display device having a plurality of display pixels arranged in a matrix and having a red color. , A green and blue image are sequentially displayed (an RGB field sequential display method), and an AC voltage is applied to each pixel to remove the influence of the video signal of the previous field. Writing a gradation signal.

Also in this configuration, since the liquid crystal display device uses liquid crystal having spontaneous polarization, high-speed response can be improved, a high frame frequency is secured, and a high-quality image with less flicker is displayed. can do. Moreover, since a triangular wave AC voltage is applied to each pixel to remove the influence of the video signal of the previous field, and then the gradation signal is written to each pixel, display burn-in can be eliminated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a configuration of an RGB field sequential display type liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device of the RGB field sequential display system has a liquid crystal display element 1
1, a liquid crystal drive unit 15, a light source system 13 disposed on the back side of the liquid crystal display element 11, and a light source drive unit 17.

The liquid crystal display element 11 is composed of a liquid crystal having spontaneous polarization (such as a ferroelectric or antiferroelectric liquid crystal), and performs a monochrome (achromatic) gradation display.

The liquid crystal drive section 15 separates the transmitted video signal into a video signal for R, a video signal for G, and a video signal for B, and stores the signal in an internal memory or the like. After applying a triangular AC voltage to the liquid crystal to eliminate the image sticking that occurred at the previous display timing, the image data corresponding to the display data for each color stored in the internal memory is applied to each pixel. The liquid crystal driving unit 15 includes a row driver 121 and a column driver 122 for writing, and the light source driving unit 17
A lighting instruction signal for instructing lighting of any one of R, 13G, and 13B is sent. The liquid crystal driving unit 15 repeats the above-described series of operations at predetermined intervals (one subfield period) and executes the same, so that the R gradation image, the G gradation image, and the B gradation image are displayed on the liquid crystal display element 11. Display a gradation image. These images are synthesized by the afterimage phenomenon on the observer's visual perception, and a color image is recognized.

The light source driving unit 17 controls the gradation image displayed by the liquid crystal display element 11 and the light source 1 in accordance with a lighting instruction signal from the liquid crystal driving unit 15 synchronized with the timing of completion of writing.
The light source system is driven so that the colors of the light irradiated by the 3R, 13G, and 13B correspond to the colors.

Next, an example of a specific configuration of the liquid crystal display element 11 will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the liquid crystal display element 11, and FIG. 3 is a plan view of one substrate (hereinafter, a lower substrate) 101 in the liquid crystal display element 11. The liquid crystal display element 11 is composed of an active matrix type ferroelectric liquid crystal display element and performs monochrome (monochrome) gradation display, and uses a thin film transistor (hereinafter, TFT) 104 as an active element. Also,
The liquid crystal display element 11 includes a pair of transparent substrates (for example, glass substrates) 101 and 102. On the lower substrate 101, transparent pixel electrodes 103 and TFTs 104 connected to the pixel electrodes 103 are formed in a matrix.

As shown in FIG. 3, on the lower substrate 101, a gate line 105 is arranged between rows of the pixel electrodes 103,
The data lines 106 are arranged between the columns of the pixel electrodes 103. The gate electrode of each TFT 104 is connected to the corresponding gate line 105, and the drain electrode is connected to the corresponding data line 106. Gate line 105
Are connected to a row driver 121 of the liquid crystal driving unit 15, and the data lines 106 are connected to a column driver 122 of the liquid crystal driving unit 15.

Further, the other substrate shown in FIG.
An upper (substrate) 102 has a transparent opposing (common) electrode 10 opposing each pixel electrode 103 disposed on the lower substrate 101.
7 are formed. The counter electrode 107 is composed of one electrode having an area covering the entire display area.

On the electrode forming surfaces of the lower substrate 101 and the upper substrate 102, alignment films 108 and 109 are provided, respectively. The alignment films 108 and 109 are made of an organic polymer compound such as polyimide, and their facing surfaces are subjected to an alignment treatment such as rubbing.

The lower substrate 101 and the upper substrate 102 are adhered to each other at the outer peripheral edge thereof via a sealing material 110.
In a region surrounded by the sealing material 110 between the substrates, a liquid crystal 111 is provided.
Is enclosed. The thickness of the layer of the liquid crystal 111 is maintained at a constant value by the sealing material 110 and the transparent gap material 112.

Above and below the liquid crystal display element 11, a pair of polarizing plates 113 and 114 are arranged.
The direction of the transmission axis 14 is set according to the orientation direction of the molecules of the liquid crystal 111.

The liquid crystal 111 is a chiral smectic liquid crystal having spontaneous polarization (such as a ferroelectric or antiferroelectric liquid crystal).
And the normal of the smectic layer is aligned with the alignment films 108, 10
A uniform layer structure is formed in the direction of the alignment treatment of No. 9.
When a voltage having a sufficiently large absolute value is applied between the opposing pixel electrode 103 and the opposing electrode 107, the liquid crystal 111 causes the liquid crystal molecules to be oriented in one direction according to the polarity of the applied voltage. Of liquid crystal molecules and a second alignment state in which liquid crystal molecules are aligned in the other direction. When a voltage whose absolute value is lower than the predetermined value is applied between the pixel electrode 103 and the counter electrode 107, the alignment state of the liquid crystal molecules is changed between the first and second alignment states according to the applied voltage. State.

The relationship between the orientation direction of the liquid crystal molecules and the optical axis direction of the polarizing plate will be described with reference to FIG. When a voltage having one polarity and an absolute value equal to or more than a predetermined value is applied, the liquid crystal 111
Means that the liquid crystal molecules have the first alignment direction 1 shown by the solid line in FIG.
11a, and becomes a first alignment state. When a voltage of the other polarity and the absolute value of which is equal to or more than a predetermined value is applied, the liquid crystal 111 has its liquid crystal molecules arranged in the second alignment direction 111b shown by a broken line in FIG. . The shift angle θ between the first alignment direction 111a and the second alignment direction 111b is determined according to the type of the liquid crystal 111.

The transmission axis 1 of one of the pair of polarizing plates 113 and 114, for example, the upper polarizing plate (hereinafter, upper polarizing plate) 114
14a is set substantially parallel to the second orientation direction 111b, and the transmission axis 113a of the lower polarizing plate (hereinafter, lower polarizing plate) 113 is set to be substantially orthogonal to the transmission axis 114a. .

The transmission axes 113a, 113a of the polarizing plates 113, 114
The liquid crystal display device in which the liquid crystal molecules 114a are set as shown in FIG. 4 has the highest transmittance (the brightest display) when the liquid crystal molecules are aligned in the first alignment direction 111a, and the liquid crystal molecules are aligned in the second alignment direction. When oriented in the direction 111b, the transmittance becomes lowest (the display is darkest).

Next, the row driver 121 and the column driver 12
2 will be described with reference to FIG.

The row driver 121 applies a gate pulse to the plurality of gate lines 105 sequentially or collectively in accordance with a drive signal from the liquid crystal drive unit 15, and the gate line 1
Scan 05. On the other hand, the column driver 122 applies a triangular wave signal to the plurality of data lines 106 when applying a triangular wave according to the driving signal from the liquid crystal driving unit 15, and applies a gradation corresponding to image data to the plurality of data lines 106 when writing an image. Apply a signal.

Next, the operation of the color liquid crystal display device of the above-structured RGB field sequential display system will be described with reference to FIG.

As shown in FIG. 5, the color liquid crystal display device of the first embodiment divides one display frame into three subframes of RGB, and displays an image of each color of RGB in each subframe.

For example, when a video signal such as a color TV signal is supplied, the liquid crystal drive section 15 separates the supplied video signal into gradation signals of RGB colors and stores them in an internal memory.

The timing immediately before the end of a certain display frame is a period of a B sub-frame (a sub-frame for displaying a blue image), and the liquid crystal display element 11 displays a B image.
Is turned on. When the display frame ends, the liquid crystal drive unit 15 controls the light source drive unit 17 to turn off the light source 13B.

Subsequently, when a new display frame is started, an R sub-frame starts as shown in FIG. R
After the start of the sub-frame, there is provided a period in which a triangular wave AC voltage is applied to all the pixels at once in order to eliminate the sticking of the display of the B image displayed immediately before the sub-frame.

When the triangular wave application period starts, the row driver 121 responds to the driving signal from the liquid crystal driving section 15 by the driving signal shown in FIG.
As shown in (A) to (C), a triangular wave application pulse is applied to all the gate lines 105 at once. All TFTs connected to all gate lines 105 by triangular wave application pulse
104 turns on. On the other hand, the column driver 122
As shown in (D), a triangular wave signal of a predetermined frequency is applied to all data lines 106. Thus, a triangular wave AC voltage is applied to all the pixel electrodes 103 via all the TFTs 104 that are turned on. The triangular wave AC voltage is applied at least for several wavelengths while all the TFTs 104 are on. During this time, the column driver 122
07, a triangular AC voltage or a fixed voltage having the opposite polarity is applied.

After starting the application of the triangular wave AC voltage,
After a predetermined period (triangular wave application period) has elapsed, the row driver 121 turns off the triangular wave application pulse applied to all the gate lines 105 as shown in FIGS. As shown in FIG. 5D, the application of the triangular wave signal applied to all data lines 106 is stopped.

Subsequently, the writing period starts, and the R display image is written into the liquid crystal display element 11. Since the writing of the display image to the liquid crystal display element 11 is performed for each row, the row driver 121 first applies a gate pulse to the gate line 105 of the first row as shown in FIG. Each TFT 104 in the first row is turned on. on the other hand,
The column driver 122 controls the liquid crystal driving unit 1 in the previous display frame.
5 receives and applies to each data line 106 a gradation signal corresponding to the R image data of the pixels in the first row, which has been separated into R, G, and B display data.
(D)). The gradation signal applied to each data line 106 is applied to each pixel electrode 103 in the first row via each TFT 104 in the first row in the ON state.

After a certain period from the turning on of each TFT 104 in the first row, the row driver 121 turns off the gate pulse applied to the gate line 105 in the first row. Accordingly, the TFTs 104 in the first row are also turned off, and the first
The voltage applied to each pixel electrode 103 in the row is held in a capacitor composed of each pixel electrode 103, a counter electrode 107, and a liquid crystal 111 interposed therebetween. Then, the alignment state of the liquid crystal molecules changes in accordance with the holding voltage, and the R black-and-white gradation image corresponding to the applied gradation signal is written to each pixel in the first row.

Subsequently, the row driver 121 is configured as shown in FIG.
As shown in (2), a gate pulse is applied to the gate line 105 in the second row to turn on the TFT 104 in the pixel in the second row, and the column driver 122 outputs a signal corresponding to the R image data of the pixel in the second row. A tone signal is applied to each data line 106 (FIG. 5D). The gradation signal applied to each data line 106 is applied to each pixel electrode 103 in the second row via each TFT 104 in the second row in the ON state.

The row driver 121 and the column driver 122 repeat the same operation until the last row as shown in FIGS. 5C and 5D. Are sequentially written.

Here, taking the pixel in the first row and the j-th column as an example, as shown in FIG. 5E, the pixel electrode 103 located at (1, j) and the opposing electrode 107 have: A triangular wave is applied during the triangular wave application period. Subsequently, each TFT 1 in the first row
While the transistor 04 is turned on by the gate pulse, a voltage corresponding to the gray scale signal applied to each data line 106 is applied to each pixel electrode 103 in the first row. When each TFT 104 is turned off, the voltage applied to each pixel electrode 103 in the first row up to that point is changed to the pixel electrode 103, the counter electrode 107, and the liquid crystal 111 between them.
Is held in the pixel capacitance composed of

When writing to all the pixels is completed and the entire black-and-white gradation image for R is displayed on the liquid crystal display element 11, the light source driving section 17 responds to the lighting instruction signal from the liquid crystal driving section 15 as shown in FIG. As shown in (F), the light source 13R is turned on until the end of the R subframe. As a result, the liquid crystal display element 11 is irradiated with R light, and the displayed black and white gradation image for R is colored R and displayed.

Next, when the sub-frame of the G image starts, as shown in FIG. 5, a triangular-wave AC voltage is applied to the pixel electrode 103 at a time, and then a black and white gradation image for G is displayed on a liquid crystal display. Write to the element 11 sequentially, and after the write is completed,
Is turned on.

Similarly, when the sub-frame of the B image starts, as shown in FIG. 5, a triangular AC voltage is applied to each pixel electrode 103 at a time, a black and white gradation image for B is written, and The lighting process of the light source 13B is sequentially performed.

Thereafter, the same operation is repeatedly executed for each display frame. In this way, by sequentially displaying three gradation images of RGB in units of one display frame,
These images are synthesized visually by the observer, and a full-color image is recognized.

According to the above configuration, a triangular wave application period is provided in each subframe, and a triangular wave AC voltage is applied to all the pixels at once. As a result, the burn-in of the display which occurred in the immediately preceding sub-frame can be eliminated at once. After that, the black-and-white gradation image is sequentially written on the liquid crystal display element 15, and after the writing is completed, the light source is turned on.
A clear color image can be displayed.

(Second Embodiment) In the first embodiment, a triangular wave AC voltage is applied to all the pixels in each subframe at once, but the present invention is not limited to this. For example, it is also possible to apply a triangular wave AC voltage to the liquid crystal in units of rows. Hereinafter, a triangular-wave AC voltage is applied to each line in each subfield, and the display burn-in generated in the immediately preceding subfield is eliminated in units of lines.
An embodiment will be described.

The physical configuration of the color liquid crystal display device of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 4, and the operation will be described below. .

As shown in FIG. 6, when a new display frame is started and an R sub-frame is started, the row driver 121 receives a drive signal from the liquid crystal drive unit 15 to cause
A triangular wave application pulse is applied to the gate line 105 of the row (FIG. 6A). Each TFT 104 connected to the gate line 105 of the first row is turned on by the triangular wave application pulse. On the other hand, the column driver 122 applies a triangular wave signal of a predetermined frequency to each data line 106 as shown in FIG. As a result, each T in the first row that is turned on
A triangular AC voltage is applied to each pixel electrode 103 in the first row via the FT 104. The triangular alternating voltage is applied at least for several wavelengths during the period when each TFT 104 in the first row is on. During this time, the column driver 122 applies a triangular AC voltage or a fixed voltage having the opposite polarity to the counter electrode 107.

When a predetermined period has elapsed since the application of the triangular wave AC voltage to each pixel electrode 103 in the first row, the row driver 121, as shown in FIG. Is turned off at one end. On the other hand, the column driver 122 is arranged as shown in FIG.
As shown in (5), the application of the triangular wave signal applied to each data line 106 is stopped. Thus, each T in the first row is
The FT 104 is turned off, and the triangular wave application period of the first row ends.

Subsequently, in order to write a display image to each pixel in the first row, as shown in FIG.
Then, a gate pulse is applied to the gate line 105 in the first row to turn on each TFT 104 in the first row. on the other hand,
The column driver 122 applies a gradation signal corresponding to the R image data to each data line 106, as shown in FIG. The gradation signal applied to each data line 106 is applied to each pixel electrode 103 in the first row via each TFT 104 in the first row in the ON state.

After a certain period from the turning on of each TFT 104 in the first row, the row driver 121 turns off the gate pulse applied to the gate line 105 in the first row. Accordingly, each TFT 104 in the first row is also turned off, and the voltage applied to each pixel electrode 103 in the first row until then is retained in the capacitor constituted by each pixel electrode 103, the counter electrode 107, and the liquid crystal 111 therebetween. Is done. Then, the alignment state of the liquid crystal molecules is changed by the held voltage, and a black and white gradation image for R corresponding to the applied gradation signal is written to each pixel in the first row.

FIG. 6E shows the voltages applied to the pixel electrode 103 and the counter electrode 107 located at (1, j). As described above, the triangular wave AC voltage is applied to the liquid crystal 111 of the pixels in the first row, and immediately after that, the gradation signal is applied, and the gradation voltage is held until the next subframe.

Thereafter, similarly, a triangular wave application period of the second row is started, a triangular wave AC voltage is applied to each pixel of the second row, and subsequently, an R black and white floor is applied to each pixel of the second row. A key image is written.

FIG. 6F shows the voltages applied to the pixel electrode 103 and the counter electrode 107 located at (2, j). As described above, a triangular AC voltage is applied to the liquid crystal 111 of the pixels in the second row, and thereafter, a gray scale signal is applied, and the gray scale voltage is held until the next subframe.

This operation is repeated for each row up to the last row, and the application of a triangular wave AC voltage to each pixel electrode 103 and the writing of a black and white gradation image for R are performed.

When the application and writing of the triangular wave are completed in row units, and the R / W grayscale image is displayed on the liquid crystal display element 11, as shown in FIG. According to the lighting instruction signal from the drive unit 15, the light source 13R
Lights up. Thereby, an R image is displayed on the liquid crystal display element 11.

Similarly, when the sub-frame of the G image starts, the application of the triangular wave and the writing of the black and white image for G are continuously performed for each row, and when the application and the writing of the triangular wave are completed to the last row, the G light source 13G Lights up. The same applies to the sub-frame of the B image.

Thereafter, by sequentially displaying the three RGB gradation images in units of one display frame, these images are synthesized visually by the observer, and a full-color image is recognized.

According to the above arrangement, a triangular-wave AC voltage is applied to each row, and subsequently, a gradation image is written, thereby eliminating display burn-in caused in the immediately preceding sub-frame on a row-by-row basis. be able to. The operation of applying the triangular waveform AC voltage and writing the gradation image is performed up to the last line, and after completion, a clear color image can be displayed by irradiating the liquid crystal display element 11 with a light source.

As described above, according to this embodiment, after each sub-frame is completed, a triangular-wave AC voltage for a plurality of wavelengths is applied to the liquid crystal 111 of each pixel of the liquid crystal display element 11. In the sub-frame, the bias of ions in the liquid crystal 111 caused by continuously applying voltages of the same polarity can be eliminated. As a result, display burn-in of an image is less likely to occur, and the burn-in of display that occurred in the previous frame can be eliminated. As a result, a high-quality color image can be displayed. Further, since the application of the triangular wave AC voltage is performed during the non-lighting period of the light source, it is possible to prevent a situation in which an unclear image due to the triangular wave is visually recognized.

Moreover, since the liquid crystal 111 having spontaneous polarization and having a high-speed response is used, it can be performed in a shorter time than the writing of an image using a TN liquid crystal or the like. Thus, a liquid crystal display device of an RGB field sequential display system with less flicker can be obtained.

The present invention is not limited to the above embodiment, and various modifications and applications are possible. For example, the configuration for applying an AC voltage is configured to be independent of the row driver 121 and the column driver 122, and scans the gate lines and the data lines with a timing signal from the liquid crystal driving unit 15. An AC voltage driver for applying an AC voltage may be provided.

FIG. 7 shows a row driver 12 having such a configuration.
1 and an example of the column driver 122 are shown.

In FIG. 7, the row driver 121 sequentially applies gate pulses to a plurality of gate lines 105,
Scanning unit 121a for scanning gate line 105
And an AC voltage driver 121b for applying an ON signal to all the gate lines 105 at once. Scanning unit 12
1a includes a shift register, a three-state type driver, and the like, like a normal row driver.

The AC voltage driver 121b applies a plurality of MOS transistors 133 for applying the power supply voltage VDD to each gate line 105, applies an ON signal to the gates of the MOS transistors 133 collectively, and outputs the output of the driver of the scanning unit 121a. Control unit 13 for setting the end to open state
4.

On the other hand, the column driver 122 applies a gradation control unit 122 a for applying a gradation signal corresponding to a display gradation to the plurality of data lines 106, and applies a triangular-wave AC voltage to all the data lines 106 collectively. AC voltage driver 122
b. The gradation control unit 122a includes a latch circuit, a three-state type driver, and the like, like a normal column driver.

The AC voltage driver 122b applies a collective ON signal to a plurality of MOS transistors 135 having one end of a current path connected to the data line 106 and the gate of the MOS transistor 135, and simultaneously controls the gradation control unit 122a.
And an AC voltage application circuit 136 for setting the output terminal of the driver to an open state and applying a triangular waveform AC voltage via the MOS transistor 135 turned on.

Next, the operation of the row driver 121 and column driver 122 having the above configuration will be described with reference to FIG.

At the start of each sub-frame, under the control of the liquid crystal drive section 15, the AC voltage drive section 121b of the row driver 121 opens the driver output terminal of the scanning section 121a and opens all the MOS transistors 1
An ON signal having a predetermined pulse width is applied to the gate 33. The ON signal turns on all the MOS transistors 133. The power supply voltage VDD is applied to all the gate lines 105 via the turned-on MOS transistors 133. Thereby, all the TFTs 104 are turned on.

On the other hand, the AC voltage application circuit 136 of the column driver 122 opens the output terminal of the driver of the gradation control unit 122a, supplies an ON signal to all the MOS transistors 135, and turns them on. Then, a triangular wave signal of a predetermined frequency is supplied to the turned on MOS transistor 1.
35 to all data lines 106.

By the above operation, all the TFTs 1 that are turned on
A triangular-wave AC voltage is applied to all the pixel electrodes 103 via the line 04.

After starting the application of the triangular wave AC voltage,
When a predetermined period has elapsed, the control unit 134 turns off the ON signal applied to the gate of the MOS transistor 133 and activates the scanning unit 121a. Further, the AC voltage application circuit 136 of the column driver 122 stops applying the triangular wave signal.

Subsequently, the row driver 121 applies a gate pulse to the gate line 105 in the first row, and the column driver 122 applies image data for pixels in the first row to the data line 106.

When the selection period ends, the gate pulse and the image data are turned off. Thereafter, the same operation is repeated for each row.

According to such a configuration, the MOS transistors 133 and 135, the control unit 134, and the AC voltage application circuit 136 are added by using the conventional configuration of the row driver and the column driver as they are, thereby realizing this embodiment. Row drivers and column drivers.

If the control unit 134 is configured to be able to control the MOS transistors 133 individually, as shown in FIG. 6, it is also possible to apply a triangular waveform AC signal and a gradation signal in units of rows. It is possible.

In the embodiment of the present invention, an example has been shown in which a triangular AC voltage is applied to each sub-frame to eliminate the image sticking of the display generated in the immediately preceding sub-frame. A period in which a triangular wave AC voltage is applied to at least one subfield may be provided.

Also, a triangular voltage has been described as an example of the voltage applied to the liquid crystal 111 in order to eliminate the image sticking in the display. Is possible, the waveform and voltage are arbitrary, and may be, for example, a rectangular wave or a sine wave.

Further, the explanation has been given using a liquid crystal display element using a TFT, but an active matrix type liquid crystal display element using an MIM (Metal-Insulator-Metal) having a structure in which a thin insulating film is sandwiched between metal thin films as an active element. Or
A simple matrix type liquid crystal display device or the like can also be used.

[0085]

As described above, according to the present invention, in the color liquid crystal display device of the RGB field sequential display system, an AC voltage is applied to each pixel before writing an image. The bias of ions can be eliminated. Therefore, display burn-in of the previous image can be eliminated, and a clear image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a structure of a color liquid crystal display device of an RGB field sequential display system according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the liquid crystal display device shown in FIG.

FIG. 3 is a plan view of a substrate on which a pixel electrode and a TFT of a liquid crystal display element are formed.

FIG. 4 is a diagram illustrating an example of a relationship between an alignment direction of liquid crystal molecules and an optical axis of a polarizing plate.

FIG. 5 is a timing chart for explaining the operation of the color liquid crystal display device of the RGB field sequential display system according to the first embodiment of the present invention.

FIG. 6 is a timing chart for explaining an operation of a color liquid crystal display device of an RGB field sequential display system according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a modified example of a row driver and a column driver.

FIG. 8 shows an example of display burning in a conventional color liquid crystal display device of the RGB field sequential display system.

[Explanation of symbols]

11: liquid crystal display element, 13R, 13G, 13B: light source, 15: liquid crystal drive unit, 17 light source drive unit, 101: lower substrate, 102: upper substrate, 103: pixel Electrode, 104 ...
TFT, 105 gate line, 106 data line, 107 counter electrode, 108 alignment film, 109
・ Alignment film, 110 ・ ・ ・ Seal material, 111 ・ ・ ・ Liquid crystal, 112 ・
..Gap material, 113 ... polarizer, 114 ... polarizer, 1
21: row driver, 122: column driver, 133, 1
35: MOS transistor, 134: control unit, 136
... AC voltage application circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/36 G09G 3/36 F term (Reference) 2H093 NA12 NA53 NA65 NB22 NC21 NC43 ND12 ND17 NE06 NF17 NF20 5C006 AA01 AA14 AA22 AF44 AF71 BB16 BB29 BF02 EA01 FA12 FA34 FA56 5C080 AA10 BB05 CC03 DD08 DD29 EE29 EE30 FF11 JJ01 JJ02 JJ04 JJ06

Claims (4)

[Claims] 1. A liquid crystal display element for interposing a liquid crystal having spontaneous polarization between electrodes forming a plurality of pixels arranged in a matrix and displaying an image by the plurality of pixels, and connecting to the liquid crystal display element. The R, G, and B images obtained by separating one color image into R (red), G (green), and B (blue) colors are sequentially displayed on the liquid crystal display device in three consecutive subfields. And at least one of the three subfields for displaying these R, G, and B images.
A driving circuit for providing a period in which a triangular wave AC voltage is applied to the electrodes of the respective pixels to display one color pixel by the three sub-fields; A light source for sequentially irradiating the liquid crystal display element with light of R, G, and B corresponding to the three subfields for displaying the R, G, and B images of the liquid crystal display element. RGB field sequential display type color liquid crystal display device. 2. The liquid crystal display device according to claim 2, wherein the driving circuit applies a triangular wave AC voltage to the liquid crystal of a plurality of pixels arranged in a matrix of the liquid crystal display element at a time or in a row. And a means for writing a gradation image for each row to a plurality of pixels arranged in the RGB.
Field sequential display type color liquid crystal display. 3. A non-lighting period is provided between periods in which the light source irradiates each of R, G, and B lights, and the driving circuit controls each of the pixels during a non-lighting period of the light source. 2. The color liquid crystal display device according to claim 1, wherein a triangular wave AC voltage is applied. 4. A color liquid crystal display device having a plurality of display pixels arranged in a matrix and using a liquid crystal having spontaneous polarization, a color of an RGB field sequential display system for sequentially displaying R, G, and B images. In the liquid crystal display device, a triangular waveform AC voltage is applied to each pixel to remove the influence of the video signal of the previous field, and then a gray scale signal is written to each pixel. Color liquid crystal display device.