JP2003122314A - Liquid crystal display device and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a bright and high-resolution field sequential liquid crystal display device. SOLUTION: This invention relates to the liquid crystal display device characterized in that a plurality of pixels are formed in a liquid crystal panel and memory is formed in each pixel. Moreover, the device is characterized in that a display information transmission means comprises display information transfer transistors and pixel control electrodes. The device is further characterized in that the pixel control electrodes for controlling the display information transfer transistors are controlled in a batch. Moreover, the invention provides a method for driving the liquid crystal display device which has the liquid crystal panel and a lighting means, and displays specified display information, and also provides a method for driving the liquid crystal display device having a step for performing field sequential driving for sequentially turning on a plurality of kinds of colors and storing the display information, and a step for transferring the display information to the pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device used for portable information terminals, liquid crystal televisions and the like.

[0002]

2. Description of the Related Art Conventionally, a method in which an active matrix element is formed is often used in a liquid crystal display device. In this method, a plurality of pixel electrodes and each pixel electrode are provided with, for example, T.
A non-linear element such as an FT transistor is formed. A source signal line for supplying a voltage signal corresponding to an image to be displayed and a gate signal line for controlling a non-linear element are formed in the vertical and horizontal directions of the screen, respectively. A selection signal is applied to a specific one of the gate signal lines, and a potential to be charged from the source signal line is supplied to the pixel electrode associated with the gate line while the selection signal is being applied. The screen is displayed by sequentially scanning the gate signal lines.

An OCB type display device has been studied as a liquid crystal display device which realizes a high speed response. The OCB type liquid crystal display device is described in "Technical Report of the Institute of Electrical Communication of Japan, EDI
98-144 page 199 ".

In this OCB type liquid crystal display device, liquid crystal is sandwiched between substrates, and transparent electrodes are formed on the substrates as voltage applying means. In the state before the power is turned on, the alignment state of this liquid crystal is a state called splay alignment. When the power of this device is turned on, a relatively large voltage is applied to the voltage applying means in a short time to change the alignment of the liquid crystal to the bend alignment state. It is a characteristic of the OCB type liquid crystal display mode to perform display using this bend alignment state. In this method, it is customary to use an active matrix method.

Generally, a color filter is usually used for color display. A color filter is a substrate on which a plurality of types of resins having a property of transmitting a selective wavelength are formed. As another method, there is also field sequential driving in which a color that lights up in a time series changes and the transmittance is adjusted in synchronization with the color. In order to display evenly and uniformly by field sequential driving, it is desirable to rewrite the display data of all pixels, that is, rewrite the screen, and then turn on the backlight of a predetermined color.

[0006]

It takes time to rewrite the screen until each gate line is sequentially scanned to complete one cycle. The longer the rewriting time, the shorter the period for lighting the backlight. As a result, there is a problem that the brightness is reduced.

[0007]

In order to solve the above problems, a liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal display panel and a lighting means for displaying predetermined display information. A liquid crystal display device is characterized in that a plurality of pixels are formed on the liquid crystal display panel, and a memory is formed for each of the pixels, by performing field sequential driving in which colors are sequentially turned on.

Further, the present invention is a liquid crystal display device having a liquid crystal display panel and a lighting means for displaying predetermined display information,
There is a period for turning off the illumination means in one field of display information, and a plurality of pixels are formed on the liquid crystal display panel,
In the liquid crystal display device, a memory is formed for each pixel.

Further, the present invention is characterized in that the display information transfer means has a display information transfer transistor and a pixel control electrode.

Further, the present invention is characterized in that the pixel control electrodes for controlling the information transfer transistors are collectively controlled.

Further, the present invention is a method of driving a liquid crystal display device which has a liquid crystal display panel and an illuminating means to display predetermined display information, and performs field sequential drive for sequentially lighting a plurality of colors to display the display information. A method for driving a liquid crystal display device, which includes a step of accumulating and a step of transferring display information to pixels.

The present invention is also a method of driving a liquid crystal display device having a liquid crystal display panel and an illuminating means for displaying predetermined display information, wherein the illuminating means is turned off within one field of the display information. A method for driving a liquid crystal display device, which includes a step of accumulating display information and a step of transferring the display information to pixels.

Further, the present invention is characterized in that the liquid crystal display panel has a low temperature polysilicon type non-linear element.

The present invention is also characterized in that the liquid crystal display panel has a reflector.

According to the present invention, the resolution of the liquid crystal display device is V.
It is characterized by being GA or higher.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A display device according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a conceptual diagram of an equivalent circuit showing a pixel structure of the present invention. 2 is a conceptual diagram showing the driving method of the present invention. Further, FIG. 3 shows the timing including the lighting of the backlight of the present invention. As shown in FIG. 1, it is a feature of the present invention that each pixel has two TFT transistors (101, 102) and further has a pixel electrode control line 103. As shown in FIG.
In the present invention, the pixel electrode control line 103 is provided after the scanning signal.
There is a selection signal 201 for applying a pulse to the pixel electrode and simultaneously transferring the signal to the pixel electrode. The characteristic of FIG. 3 is that
The backlight is still on during scanning, so there is no loss of brightness.

For comparison, a conventional pixel structure is shown in FIG. 4, a conventional drive waveform is shown in FIG. 5, and a timing chart is shown in FIG. In the conventional method, the gate line 104 including a plurality of pixels is formed.
Then, the scanning signal 202 is sequentially applied to the TFT transistor 101, which is a non-linear element connected to the gate line 104. A potential to be written in a predetermined pixel 107 is supplied from the source line 105 at the timing of applying the selection signal to the gate line. When the pixel is fully charged,
The potential of the gate line is set to the OFF state 203, and scanning for applying the selected waveform to the next gate line is performed. While scanning a series of gate lines and rewriting the display information, the backlight is turned off (FIG. 6). After the rewriting of the entire screen is completed and the liquid crystal responds sufficiently, the backlight of a predetermined color is turned on and a predetermined display is performed. After that, the backlight is turned off and rewriting of the next screen is started.

If the backlight is turned on during this writing period, an inappropriate picture will be displayed because the previous screen remains at the lower part of the screen, and the upper part and the lower part of the screen will be displayed. Problems that differ in appearance also occur.

In the field sequential driving, there is a problem in that it is desired to extend the lighting time of the backlight as much as possible to improve the brightness. However, there is a problem that the lighting time is shortened when a relatively long writing time is consumed as in the conventional example. Of the 4 ms corresponding to 1 frame display for 4 colors, 3 ms is consumed for rewriting the screen, and the display may be performed for the remaining 1 ms.

Therefore, in the liquid crystal display device of the present invention, the memory 106 is formed in each pixel, and the step 301 for accumulating the display information in this memory and the period 302 for writing the display information in the pixel electrode are separated to reduce the writing time. Achieved shortening.

As shown in FIG. 1, a memory 106 is formed in each pixel of the liquid crystal display device of the present invention. In the present embodiment, the invention is a dynamic memory including the capacitor Cmem 106 and the transistor 101 that controls the charging thereof. Although there is a problem that the structure becomes complicated, static memory may be used.

As shown in FIG. 2, the gate line 104 scans similarly to the conventional example, and the display information is supplied from the source line 105 accordingly. The present embodiment is different from the conventional example in that the display information (that is, the write potential supplied from the source line 105) is temporarily charged in the memory 106. Here, the pixel electrode 107 and the memory 106 are connected by the transistor 102, but in the period 301 in which the memory is sequentially charged, the pixel electrode 107 and the memory 106 are electrically cut off by turning off the transistor 102. As a result, the previous display information is left as it is on the pixel electrode 107, and the display is not affected even during the memory writing period. Therefore, the backlight may be on. Therefore, there is an advantage that the lighting time of the backlight can be kept long.

When the memories of all the pixels are completely charged, the potential of the memories is supplied to the pixel electrodes in the next step. At this time, the memory 106 and the pixel electrode 107
The selection signal 201 is supplied to the pixel control electrode 103 so as to turn on all the transistors 102 connected to and.

The present invention makes the pixel structure more complicated than ever. For this reason, it is preferable to form a transistor using a low temperature polysilicon device rather than forming a TFT from amorphous silicon.

Further, in the present invention, the data transfer from the memory 106 to the pixel electrode 107 is carried out all at once, but this may be divided into a plurality of times. At this time, the 201 pulse shown in FIG. 2 may be divided into a plurality of portions to divide the pixel control electrode 103 into a plurality of blocks.

Specific structures of the liquid crystal display device according to the present invention shown in FIGS. 1 to 3 are shown in FIGS. FIG. 8 is a plan view of the liquid crystal display device, and FIG. 9 is a sectional view taken along line AA of the same. As shown in FIG. 8, the gate electrode line 801 and the source electrode line 808 intersect, and a charge control transistor 805 is provided near the intersection. The charging transistor 805 corresponds to the memory charging TFT 101. The charge control transistor 805 is connected to the memory capacitor electrode 804 provided in parallel with the gate electrode line 801. The memory capacity electrode 804 corresponds to the memory 106. A common electrode 802 is provided below the memory capacitance electrode 804, and thus the common electrode 80 is provided.
2 and the memory capacity electrode 804 form a capacitor.

0V is always applied to the common electrode 802, and the write voltage supplied from the source electrode line 808 to the memory capacity electrode 804 through the charge control transistor 805 is once sent to the memory capacity electrode 804.
Will be accumulated.

Gate electrode line 801 and pixel control electrode 803
Although the common electrode 802 and the memory capacitance electrode 804 are sandwiched between and, the memory capacitance electrode 804 and the pixel electrode 807 are connected by the transfer transistor 806. This transfer transistor 806 is a pixel transfer TF.
This transfer transistor, which corresponds to T102, is turned on by applying a drive voltage to the pixel display electrode 803 provided in parallel to the gate electrode line 801, and the write voltage once stored in the memory capacitor electrode 804 is turned on. It is sent to the pixel electrode 807.

The present invention is effective for a high-definition display having a large number of gate lines and having a long scanning time. Specifically, it is effective when performing field sequential driving on a display having a resolution of VGA (640 × 480) or higher.

Although the TFT transistor is used in the present invention, an MIM type element may be used. These are generally called non-linear elements.

When a plurality of TFT transistors are formed as in the present invention, the transmissive type has a problem that the aperture ratio is lowered. However, this problem hardly occurs in the reflective type or the semi-transmissive type. This is because in the reflective type, the TFT structure and the memory may be formed under the reflector. INDUSTRIAL APPLICABILITY The present invention is effective for a reflection type or semi-transmission type device having a reflection plate. In this case, in order to perform field sequential driving, a front light type illumination means is desirable. Further, a light emitting device such as an organic EL may be used.

(Embodiment 2) In this embodiment, a method of inserting a blanking period is adopted in order to improve the visibility of a moving image and further speed it up. In order to improve the visibility of moving images, a black screen may be inserted as in JP-A-11-109921, but JP-A-9-325715.
The backlight may blink as in the publication. The latter is preferable as an actual device because the power consumption does not increase significantly.

However, if it takes a lot of time for scanning and writing in order to blink the backlight, there is a problem that the lighting period of the backlight cannot be sufficiently secured. Therefore, the present invention has the same pixel structure as that of FIG. 1 and repeats the process of transferring the scanning signal and the electric charge of the memory as shown in FIG. In order to combine this with the blinking system of the backlight, the blinking sequence as shown in FIG. 7 was used. Here, a period 301 for scanning and a period 30 for transferring data to pixels
Since 2 is separated, the backlight may be turned on during the scanning period. As a result, it can be applied to the blinking system of the backlight, improving the visibility of moving images.

In this embodiment, a liquid crystal panel having a light source using a fluorescent tube and a color filter is used.

In the present invention, there is less restriction on the period during which the backlight is turned on. Therefore, a mechanism for adjusting the backlight lighting period and adjusting the time width of the black screen for improving the visibility of the moving image may be introduced. If the black screen period is long, the visibility of the moving image is improved, but the brightness is reduced. On the contrary, when the black period is short, it is bright but the visibility of the moving image is deteriorated. Therefore, a mechanism for switching between the brightness priority mode and the moving image visibility priority mode is provided. Japanese Patent Application No. 2000-12
The 7102 was provided with this switching mechanism, but it could be easily realized by using the present invention. Conventionally, there is a problem that the transistor size needs to be increased more than usual and the transistor size is increased.

[0037]

As described above, according to the present invention, a bright field-sequential liquid crystal display device having a high resolution can be realized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a pixel structure of a liquid crystal display device of the present invention.

FIG. 2 is a conceptual diagram showing a driving method of a liquid crystal display device of the present invention.

FIG. 3 is a conceptual diagram showing a driving sequence of the liquid crystal display device of the present invention.

FIG. 4 is a conceptual diagram showing a pixel structure of a conventional liquid crystal display device.

FIG. 5 is a conceptual diagram showing a driving method of a conventional liquid crystal display device.

FIG. 6 is a conceptual diagram showing a drive sequence of a conventional liquid crystal display device.

FIG. 7 is a conceptual diagram showing a drive sequence of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 8 is a plan view showing a pixel structure of a liquid crystal display device of the present invention.

FIG. 9 is a cross-sectional view showing a pixel structure of a liquid crystal display device of the present invention.

[Explanation of symbols]

101 Memory charging TFT 102 pixel transfer TFT 103 pixel control electrode 104 gate line 105 source line 106 memory 107 pixels 201 selection signal 202 scanning signal 203 Scan stopped state 301 scanning period 302 Transfer period 801 Gate electrode wire 802 Common electrode (Vcom) 803 Pixel control electrode 804 Memory capacity electrode 805 Charge control transistor 806 transfer transistor 807 pixel electrode 808 Source electrode wire

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/34 G09G 3/34 J F term (reference) 2H093 NC34 NC35 NC42 NC43 ND01 ND08 ND52 NE06 5C006 AA22 AF42 BB16 BB29 BC20 EA01 5C080 AA10 BB05 CC03 DD30 FF11 JJ03 JJ04 JJ06 KK07 KK43

Claims (10)

[Claims] 1. A liquid crystal display device having a liquid crystal display panel and illumination means for displaying predetermined display information, wherein field sequential driving is performed to sequentially light a plurality of colors, and a plurality of pixels are provided on the liquid crystal display panel. And a memory is formed for each pixel. 2. A liquid crystal display device having a liquid crystal display panel and an illuminating means for displaying predetermined display information, wherein the illuminating means is turned off within one field of the display information, and the liquid crystal display panel has A liquid crystal display device, wherein a plurality of pixels are formed, and a memory is formed for each of the pixels. 3. The liquid crystal display device according to claim 1, further comprising a display information transfer unit that forms a pixel electrode for each pixel and transfers display information from the memory to the pixel electrode. 4. The liquid crystal display device according to claim 3, wherein the display information transfer means has a display information transfer transistor and a pixel control electrode. 5. A liquid crystal display device according to claim 4, wherein the pixel control electrodes for controlling the information transfer transistors are collectively controlled. 6. A method of driving a liquid crystal display device having a liquid crystal display panel and a lighting means for displaying predetermined display information, the method comprising field sequential driving for sequentially lighting a plurality of colors to accumulate the display information. And a method for driving a liquid crystal display device, which comprises the step of transferring display information to pixels. 7. A method of driving a liquid crystal display device having a liquid crystal display panel and a lighting means for displaying predetermined display information, wherein the lighting means is turned off within one field of the display information, and the display information is displayed. A method of driving a liquid crystal display device, which comprises the steps of accumulating and transferring display information to pixels. 8. The liquid crystal display device according to claim 1, wherein the liquid crystal display panel has a low temperature polysilicon type non-linear element. 9. The liquid crystal display device according to claim 1, wherein the liquid crystal display panel has a reflection plate. 10. The liquid crystal display device according to claim 1, wherein the resolution of the liquid crystal display device is VGA or higher.