JP2000235371A - Liquid crystal display device with built-in peripheral drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress flickering on a screen caused by the interaction between display patterns and a driving system in a liquid crystal display device with built-in peripheral driving circuit. SOLUTION: One pixel is composed of plural subpixels (pixel transistors 3a and 3b, pixel electrodes 4a and 4b, liquid crystal layers 10a and 10b and storage capacitors 8a and 8b), and positive and reversed polarity liquid crystal driving are conducted to respective subpixels of the pixel. Thus, flickering of the screen is remarkably suppressed and a very high quality picture is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor circuit, and more particularly to a liquid crystal display device having a built-in peripheral driving circuit using a polysilicon thin film transistor.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a main part of a conventional peripheral drive built-in type liquid crystal display device. It has a built-in peripheral drive circuit using a polysilicon thin film transistor. In FIG. 5, 1 is a scanning line, 2 is an image signal line, and pixel transistors 3 and pixel electrodes 4 are arranged in a matrix on a screen portion.
(Although not shown, there is also a storage capacity, etc.). The scanning line 1 is a first peripheral driving circuit (scanning signal circuit: internal configuration of the circuit, a circuit diagram is not shown) 8
, And the image signal line 2 is connected to the transfer gate transistor 5 for signal writing. The transfer gate transistor 5 for signal writing operates as a transfer gate transistor by a control signal from the second peripheral drive circuit 7 (internal configuration of the circuit; a circuit diagram is not shown), and the image signal from the signal line 6 is converted to an image. It is configured to be written to the signal line 2. In the figure, one signal line 6 is shown for a monochrome display panel. However, in the case of color display, three signal lines 6 are used in parallel corresponding to three colors of RGB. Although not shown, a liquid crystal display device is constituted by a counter substrate having a liquid crystal and a counter electrode, peripheral members such as a backlight and a polarizing plate, and an external circuit portion for shaping an input signal. For example, the magazine “Flat Panel Display 19”
94 "(published by Nikkei BP December 10, 1993) 1
90 pages to 193 pages.

Recently, in addition to the type in which an image signal voltage for driving a liquid crystal as shown in FIG. 5 is externally input, digital image data information is input, and digital-to-analog conversion is performed inside a second peripheral driving circuit. Some will cause

FIG. 6 is a circuit diagram (1) of the pixel section of FIG.
2 is a layout diagram (2) of a polysilicon thin film transistor substrate corresponding to the pixel portion, and does not include a liquid crystal layer and a counter electrode. As shown in FIG. 6, a storage capacitor 8 is connected to the pixel electrode 4. Reference numeral 9 denotes a common line connected to the storage capacitor over the entire screen. Reference numeral 11 denotes a counter electrode formed on the counter substrate, and the liquid crystal layer 10 is interposed between the counter electrode and the pixel electrode 4. The storage capacitor 8 is formed at an overlapping portion between the pixel electrode 4 and the common line 9. Note that the same portions corresponding to those in FIG. 5 are denoted by the same reference numerals and description thereof is omitted.

FIG. 7 shows a liquid crystal display signal for driving a conventional liquid crystal display device. In FIG. 7, Vlc is an image signal applied to one image signal line 2. Vc
om is the potential of the counter electrode 11. Vg is a gate signal applied to one scanning line 1. When Vg is at a high level, the pixel transistor 3 connected thereto is turned on, and Vlc is transmitted to the corresponding pixel electrode 4. At this time, the liquid crystal is driven by a potential difference of Vsig = Vlc-Vcom, and light and dark display corresponding to each signal intensity is performed for each pixel. The liquid crystal is driven at an AC potential with respect to the counter electrode potential Vcom. The polarity with respect to Vcom is the polarity opposite to the polarity as shown in the figure. At this time, each pixel electrode is driven alternately with a signal of a positive polarity and a signal of a reverse polarity.

FIG. 8 shows a driving state (polarity state) diagram of a liquid crystal layer of a typical pixel section which is currently shown in the market and described in FIGS. 5 to 7, and shows a part of the arrangement of pixels. Usually, about 30 screen data are rewritten per second. This figure shows the driving state of the liquid crystal layer corresponding to the one screen data and the driving state of the liquid crystal layer corresponding to the next screen data. ing. Each time the image data is rewritten, the polarity is reversed for each pixel. Here, the left side of FIG. 8 shows the polarity when one image data is displayed, and the right side shows the polarity when the next image data is rewritten.

FIG. 8A shows a so-called 1H inversion drive, in which pixels having a positive polarity and a reverse polarity are arranged at every horizontal stage.
FIG. 8 (2) shows what is called 1V inversion driving, in which pixels having a positive polarity and a reverse polarity are lined up for each stage in the vertical direction. And FIG.
(3) is a so-called dot inversion drive in which pixels having a positive polarity and a reverse polarity are arranged in a staggered arrangement (checkered pattern).
Incidentally, the optical response of the liquid crystal, including the change with time, is slightly different between the case of the positive polarity and the case of the opposite polarity. In these displays, the flicker of the screen can be suppressed by configuring the pixels adjacent to each other in one piece of screen data to have the same amount of transmitted light and to have both forward and reverse polarities. Conversely, if there is an area where only pixels of the same polarity are present in one piece of screen data, remarkable flicker is felt in that area, and the image quality is extremely deteriorated.

[0008]

However, FIG.
According to the conventional circuit configuration of the pixel portion described with reference to FIG. 6 and the driving method of the liquid crystal display device described with reference to FIGS. 7 and 8 for the pixel portion, there are the following problems. That is, flicker cannot be suppressed in all display images, and flicker may be noticeable depending on the type of display image. Particularly, in recent years, this problem has occurred in a liquid crystal display device used for a notebook personal computer, an information terminal, or the like where the liquid crystal display device is frequently used. Normally, the display data of the screen is internally processed as digital image information as screen dot data (luminance data of points in a matrix).
Therefore, the most efficient image display is achieved by using a liquid crystal display device having a pixel arrangement corresponding to these image information dots on a one-to-one basis. For example, a liquid crystal display having an SVGA dot (pixel) array is most suitable for displaying SVGA image information. When a mismatched VGA or XGA data is displayed on this SVGA liquid crystal display device, it is displayed for data correction. The image is distorted.

[0009] However, in the case of a display that handles dot data, it is often the case that light and shade are displayed every other dot data and a checkered pattern is displayed. This display section actually appears on a standard Windows display screen.
At this time, the pixels corresponding to one-to-one are adversely affected, and the portion flickers, resulting in a very unsightly display.

[0010] This is because the pattern of the image information matches the pattern of the forward and reverse polarities of one screen data shown in FIG. 8, and when viewed one image data at a time, the transmitted light of one kind of pixel is displayed in the display part. This is because a large part of the light is occupied by a significant flicker.

The above is a case of a liquid crystal display device used for a personal computer, an information terminal, or the like. If the driving polarity pattern of the liquid crystal layer of the pixel portion is aligned with the screen to be displayed even with a general image, the screen flickers. I do. For example, 1H
In the case of inversion drive or 1V inversion drive, when a stripe line is displayed or when a display body is moved, the screen flickers if the conditions are met. For example, it is likely to occur in a camera-integrated video movie or the like in which the eyes sometimes follow one polarity.

In the present invention, attention is paid to this point, and high quality image display is achieved by suppressing flickering of the screen due to the pattern of the driving state (polarity) of the liquid crystal layer of the pixel portion being aligned with the screen to be displayed. The purpose is to do.

[0013]

According to the present invention, in order to solve the above-mentioned problems and to achieve the object, a potential applied to a liquid crystal with respect to a counter electrode potential is a sub-pixel having a polarity opposite to that of a positive sub-pixel. A pixel composed of both sub-pixels consisting of pixels,
A liquid crystal display device with a built-in peripheral driving circuit for generating two types of liquid crystal driving signals of positive polarity and reverse polarity for the sub-pixel in a display panel substrate.

According to the present invention, as long as one pixel is composed of a plurality of sub-pixels and each sub-pixel of one pixel displays substantially the same luminance (amount of transmitted light), Even if there is a large amount of screen data, the sub-pixels of the same polarity (transmitted light amount) with the positive polarity and the sub-pixels with the opposite polarity are present close to each other, and the flicker of the screen is significantly suppressed. Images can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has a pixel having both positive and negative polarity sub-pixels in which the potential applied to the liquid crystal with respect to the counter electrode potential is a reference. A liquid crystal display device with a built-in peripheral driving circuit for generating two types of liquid crystal driving signals of a positive polarity and a reverse polarity for the sub-pixel in a display panel substrate. As for the number and arrangement of the sub-pixels, it is sufficient that the pixel electrodes of the positive polarity and the opposite polarity have the same area, but the number of image signal lines is doubled and divided vertically, or the number of scanning lines is doubled. It is reasonable to divide horizontally. In particular, in a liquid crystal display device with a built-in peripheral driving circuit using polysilicon, a signal of the opposite polarity can be generated in the peripheral driving circuit. Further, even if the number of image signal lines and scanning lines is increased, the burden on the outside is reduced, which is convenient for realizing the present invention.

One pixel is composed of a plurality of sub-pixels,
Since the sub-pixels of one pixel display substantially the same luminance (the amount of transmitted light), the same sub-pixel of the same polarity and the sub-pixel of the opposite polarity are always used for any screen data. Since they exist close to each other, flicker on the screen is significantly suppressed, and a very high-quality image can be obtained.

(Embodiment 1) FIG. 1 is a circuit configuration diagram (1) of a pixel portion of a liquid crystal display device with a built-in peripheral driving circuit according to Embodiment 1 of the present invention, and a polysilicon thin film transistor substrate corresponding to the pixel portion. It is a layout diagram (2),
The liquid crystal layer and the counter electrode are not included.

In FIG. 1A, 1a and 1b are positive and sub scanning lines, 2 is an image signal line, 3a and 3b are pixel transistors for sub pixels, and 4a and 4b are pixel electrodes for sub pixels. . The pixel electrodes 4a and 4b are also connected to storage capacitors 8a and 8b, respectively. Reference numeral 9 denotes a common wiring connected to the storage capacitors over the entire screen. Reference numeral 11 denotes a counter electrode formed on the counter substrate, and the pixel electrode 4a or 4
b, the liquid crystal layer 10a or 10b is interposed. The pixel transistors 3a and 3b having the above configuration are polysilicon thin film transistors formed at a low temperature (substrate heating temperature at the time of fabrication is approximately 600 ° C. or less), and the pixel electrodes 4a and 4b
It is a pixel electrode made of TO. Here, the storage capacitors 8a and 8
“b” is formed at a portion where the pixel electrode 4 a or 4 b and the common line 9 overlap. This pixel configuration is incorporated in a liquid crystal display device having a built-in peripheral drive circuit of a polysilicon thin film transistor in which an image memory for one scanning line is built in a peripheral drive circuit.

Next, the operation of the pixel section having the above configuration will be described. First, the selection time of one scanning line is set to half the normal time, a positive liquid crystal drive signal is written to the upper half sub-pixel, and then the lower half sub-pixel is selected. Write the opposite polarity liquid crystal drive signal to
Perform double speed drive.

FIG. 2 shows the driving state (polarity state) of the liquid crystal layer corresponding to one screen data in the pixel portion of FIG. 1, (1) shows case 1 and (2) shows case 2. In both cases, the left side in FIG. 2 shows the polarity when displaying one image data, and the right side shows the polarity when rewriting the next image data. As can be seen from FIG. 2, the polarity is reversed from left to right every time the next image data is rewritten, on a pixel-by-pixel basis. Here, two examples are shown as arrangements of positive polarity and reverse polarity.

One pixel is composed of a plurality of sub-pixels,
Since the sub-pixels of one pixel display substantially the same luminance (the amount of transmitted light), the same sub-pixel of the same polarity and the sub-pixel of the opposite polarity are always in proximity regardless of the screen data. Screen flickers
Is significantly suppressed, and a very high-quality image can be obtained.

(Embodiment 2) FIG. 3 is a circuit diagram (1) of a pixel portion of a liquid crystal display device with a built-in peripheral driving circuit according to Embodiment 2 of the present invention, and a polysilicon thin film transistor substrate corresponding to the pixel portion. FIG. 2 is a layout diagram (2), and does not include a liquid crystal layer and a counter electrode.

In FIG. 3, 1c is a scanning line, 2c and 2d
Is a positive and sub image signal line, 3c and 3d are pixel transistors for sub-pixels, and 4c and 4d are pixel electrodes for sub-pixels.
The pixel electrodes 4c and 4d are also connected to storage capacitors 8c and 8d, respectively, and 9 is a common wiring connected to the storage capacitors over the entire screen. Reference numeral 11 denotes a counter electrode formed on the counter substrate, and the liquid crystal layer 10c or 10d is sandwiched between the counter electrode 11 and the pixel electrode 4c or 4d. Here, the storage capacity 8
c and 8d are formed in an overlapping portion of the pixel electrode 4c or 4d and the common wiring 9. This pixel configuration is incorporated in a liquid crystal display device having a built-in peripheral driving circuit using polysilicon thin film transistors.

Next, the operation of the pixel section having the above configuration will be described. First, drive signals having different polarities are transmitted to the left half sub-pixel and the right half sub-pixel.

FIG. 4 shows the driving state (polarity state) of the liquid crystal layer corresponding to one screen data in the pixel portion of FIG. 3, (1) shows case 3 and (2) shows case 4. In both cases, the left side of FIG. 4 shows the polarity when one image data is displayed, and the right side shows the polarity when the next image data is rewritten. As can be seen from FIG. 4, the polarity is reversed from left to right every time the next image data is rewritten, in units of pixels. Here, two examples are shown as arrangements of positive polarity and reverse polarity.

One pixel is composed of a plurality of sub-pixels.
Since the sub-pixels of one pixel display substantially the same luminance (the amount of transmitted light), the same sub-pixel of the same polarity and the sub-pixel of the opposite polarity are always in proximity regardless of the screen data. Screen flickers
Is significantly suppressed, and a very high-quality image can be obtained.

In the first and second embodiments, signals of opposite polarities are created by a peripheral drive circuit arranged around the screen portion as shown in FIG. 5, but in recent years, there are also developments in applications such as a reflection type liquid crystal display device. In this case, the peripheral drive circuit does not necessarily need to be arranged outside the screen. Therefore, a signal generator having a reverse polarity can be provided for each pixel region. Therefore,
In the present invention, this is also regarded as a part of the peripheral drive circuit.

[0028]

As described above, according to the present invention, the potential applied to the liquid crystal with respect to the potential of the counter electrode is positive,
It is composed of both sub-pixels composed of sub-pixels of opposite polarity, and generates two kinds of liquid crystal driving signals of positive polarity and reverse polarity for these sub-pixels on the display panel, thereby significantly suppressing flickering of the screen. Thus, a very high quality image can be obtained.

[Brief description of the drawings]

FIG. 1A is a circuit configuration diagram of a pixel portion of a liquid crystal display device with a built-in peripheral driving circuit according to Embodiment 1 of the present invention;
(2) is a layout diagram of a polysilicon thin film transistor substrate corresponding to the pixel portion.

FIG. 2 is a driving state diagram of a liquid crystal layer corresponding to one screen data in the pixel unit of FIG. 1;

FIG. 3A is a circuit configuration diagram of a pixel portion of a liquid crystal display device with a built-in peripheral driving circuit according to Embodiment 2 of the present invention;
(2) is a layout diagram of a polysilicon thin film transistor substrate corresponding to the pixel portion.

4 is a driving state diagram of a liquid crystal layer corresponding to one screen data in the pixel unit of FIG. 2;

FIG. 5 is a circuit configuration diagram of a main part of a conventional peripheral drive built-in type liquid crystal display device.

6A is a circuit diagram of a pixel unit in FIG. 5, and FIG. 6B is a layout diagram of a polysilicon thin film transistor substrate corresponding to the pixel unit.

FIG. 7 is a liquid crystal display signal diagram for driving a conventional liquid crystal display device.

FIG. 8 is a driving state diagram of a liquid crystal layer of a typical representative pixel section in the related art.

[Explanation of symbols]

 1, 1a, 1b, 1c Scanning line 2, 2c, 2d Image signal line 3, 3a, 3b, 3c, 3d Pixel transistor 4, 4a, 4b, 4c, 4d Pixel electrode 5 Transfer gate transistor for signal writing 6 Signal wiring 7 Second peripheral drive circuit 8 First peripheral drive circuit (scan signal circuit) 9 Common wiring 10, 10a, 10b, 10c, 10d Liquid crystal layer 11 Counter electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H092 JA24 KA04 MA29 NA01 PA06 PA11 2H093 NA34 NA61 NC34 ND10 5C006 AC27 AF42 BB14 BB16 BC03 BC12 FA23 FA25 5C080 AA10 BB05 DD06 EE28 FF11 FF13 JJ02 JJ03 JJ04 JJ05 JJ05

Claims (5)

[Claims] An electric potential applied to the liquid crystal with reference to an opposing electrode electric potential has a pixel composed of both sub-pixels including a sub-pixel having a positive polarity and a sub-pixel having a reverse polarity. A liquid crystal display device with a built-in peripheral driving circuit, wherein two types of liquid crystal driving signals having a positive polarity and a reverse polarity are generated in a display panel substrate. 2. The liquid crystal display device with a built-in peripheral driving circuit according to claim 1, wherein the liquid crystal display device is a circuit made of polysilicon thin film transistors. 3. A liquid crystal display device with a built-in peripheral driving circuit according to claim 1, wherein two kinds of liquid crystal driving signals having a positive polarity and a reverse polarity are generated in said pixel portion. 4. A single pixel is provided with two primary and secondary scanning lines,
2. A liquid crystal display device with a built-in peripheral driving circuit according to claim 1, wherein one sub-pixel is provided for each of the sub-pixels, and two types of liquid crystal driving signals having a positive polarity and a reverse polarity are written in each of the sub-pixels. 5. A single pixel is provided with two image signal lines of positive and sub, one sub-pixel is provided for each, and two kinds of liquid crystal driving signals of positive polarity and reverse polarity are written in each pixel. The liquid crystal display device with a built-in peripheral driving circuit according to claim 1.