JPS62143088A - Display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a display device that provides display with good image quality.

[Background of the invention]

Conventionally, cathode ray tubes have been widely used as devices for displaying characters or television images, but in recent years, dot matrix tubes using liquid crystals, EL, etc. have been used because they have the advantage of being able to reduce the depth of the display device. Display devices have started to attract attention.

However, in the case of this dot matrix type display device, when the number of dots (pixels) is increased in an attempt to obtain a resolution equivalent to that of a cathode ray tube, crosstalk occurs and the contrast of the image becomes significant, especially in the case of a time division type liquid crystal display device. Getting worse. In order to prevent this, a so-called active matrix type display device in which each pixel is provided with a switching element such as a thin film transistor (hereinafter abbreviated as TPT) or a thin film diode has been proposed and is being developed.

In addition, prior art related to the specific example of the display device in the present invention includes Patent Application Publication No. 18886 of 1972 and 1972 IEEE C0NFERENCE RE-C of the Display Device Society of Japan.
ORD OF 1972 C0NFERENCE ON
DISPLAY DE-vrcr:s) pages 64-66
“Design of LCD color TV panel” (“DESrGN”)
OF A LIQUID CRYSTAL C0-LO
RTV PANEL') is introducing a technology that stacks thin film transistors (TPT) inside a liquid crystal panel.

However, in this type of display device, the signal line and scanning line that supply signals to each TPT are formed of a metal film, the signal line is formed in the same layer as the pixel electrode, and the scanning line is also formed of a metal film. Since the metal film has poor light transmittance, it has been impossible to form both of them overlappingly with the pixel electrode. Therefore, the size of the pixel electrode is determined by the pitch of the signal line and the scanning line, which naturally limits the aperture ratio of the pixel.

[Purpose of the invention]

An object of the present invention is to provide a display device that improves the aperture ratio of pixels and provides a bright screen.

Another object of the present invention is to provide a display device that can provide clear images.

[Summary of the invention]

According to one embodiment of the present invention, by forming the gate electrode of a thin film transistor and its scanning line with a low resistance film such as an amorphous silicon film, the pixel electrode can be formed overlappingly on the scanning line. A display device with improved aperture ratio is provided.

[Embodiments of the invention]

Next, embodiments of the present invention will be described in detail using the drawings.

1 to 4 are diagrams illustrating an active matrix type display device according to the present invention.

In FIG. 1, 1 is a pixel, 2 is a thin film switching element such as TPT, 101, 102 . ...is TPT
'Scanning lines for controlling on/off of ', 201, 2
02. ... are signal lines that supply image information. Fig. 2 is a diagram showing a cross-sectional structure of TFT 2 incorporated into a liquid crystal display element, and Fig. 3 is a plan view thereof, in which 3 is a substrate, 4 is a gate, 5 is a gate insulating film, 6 is a semiconductor, and 7 is a top view. drain, 8
9 is a source, and 9 is a pixel electrode forming a part of the pixel 1. Figure 4 shows the symbols of TPT, 4 is gate, 7 is drain, 8 is source, 20 is alignment film, 21 is liquid crystal, 22 is alignment film, 23 is electrode, 24 is filter, 25 is transparent glass It's on the board. By changing the voltage applied to gate 4,
The electrical resistance between the drain 7 and source 8 changes to act as a switch.

Next, a display method using this method will be explained. First, scan line 1
By applying an appropriate voltage to 01, one horizontal row of TPTs connected to it are turned on for a certain period of time.

At this time, all other TPTs are turned off. In this state, the signal lines 201, 202. An image information signal is supplied from φ to turn the selected pixel on, off, or in an intermediate state. In this case, from the signal line 201 to 202, 203 degrees...
A method in which signals are sequentially supplied in the order of . is called dot sequential scanning, and a method in which signals are simultaneously supplied from all signal lines 201, 202, 203, . . . is called line sequential scanning. In the case of point sequential scanning, since the signal input time is short, a TPT with high switching speed is required.

Next, the TPT in the column of scanning line 101 is turned off, the TPT in column 102 is turned on, and image signals are similarly supplied. Still images or moving images can be displayed by similar scanning.

The above is a case of black and white display, but in the case of color display, color pixels emitting light in each of the three primary colors are arranged as shown in FIG. In this case, one set of three primary color pixels of red (R), green (G), and blue (B) forms one color pixel 30m. In order to display, for example, a color video image by line-sequential scanning on such a display panel, first the input video image signal 10 is separated into three primary color signals by a color separation circuit 11, as shown in FIG. and separate analog memories 12B,
12G.

Temporarily memorize it in 12H. Then, all TPTs (one horizontal row) connected to the first scanning line are turned on, and image information of the first scanning line is supplied from each analog memory to each color pixel.

Thereafter, scanning is repeated in the same manner, and a color image is displayed.

However, when color pixels are arranged as shown in Figures 5 and 6, each color pixel forming one color pixel is
Since they are arranged in rows, it is difficult to increase the pixel density (resolution) in the horizontal direction. That is, to obtain the same resolution as in monochrome display, it is necessary to triple the pixel density in the horizontal direction. Therefore, scan lines 101, 102 . The number of signals #J201.202. is the same as in the case of black and white display. The number of -... will be tripled.

In a normal black and white display device, the number of signal lines is greater than the number of scanning lines, and the signal line density is higher than the scanning line density. Moreover, not only does it become difficult to connect to the drive circuit, but the total number of wiring lines, which is the sum of the number of scanning lines and the number of signal lines, increases significantly, reducing the yield of the matrix array.

Further, the shape of one pixel becomes significantly vertically long. That is, in FIG. 3, the signal lines 201, 202, . . . . - is long, and the scanning line 101.102. The sides that are close to ... become shorter. As a result, as is clear from FIG. 2, the scanning line 101 connected to the gate 4 of the TFT 2,
102. ... is insulated from the pixel electrode 9 by the insulating film 5, so even if they overlap as shown in FIG. 3, there will be no short circuit, but the signal line 2 connected to the source 8 of the TFT 2
Since the pixel electrodes 01, 202, . Therefore, the pixel electrode 9 and the signal lines 201, 202 . The distance tm between the pixel electrode 9 and scanning &! 101.10
2. As the distance tg between the pixels becomes longer, the aperture ratio (ratio of total pixel area/total area) becomes smaller and the screen becomes darker.

Therefore, in the present invention, as shown in FIG.
01.102. φ...wo is formed using an amorphous silicon n-layer film.

According to such a configuration, since the amorphous silicon n layer has good light transmittance, the gate 4 and the scanning lines 101, 102 .・
... The pixel electrode 9 can be formed in an overlapping manner by extending upward, thereby increasing the surface area of the pixel electrode 9 and expanding the surface area of the pixel. - For example, when a flat display with a pixel pitch of 0.36 m is manufactured, the aperture ratio can be greatly improved to about 6% compared to that shown in FIG. 3, making the screen brighter. Furthermore, the scanning lines 101, 102 . ...Since the pixel electrode 9 is expanded to the top, adjacent pixel electrodes 9 come close to each other, and a clear image with high resolution can be obtained. Furthermore, signal lines 101, 102 . −
By using 72 layers of amorphous silicon,
This amorphous silicon 72 layer has a low resistivity, so
The signal response speed can be improved at the same time.

〔Effect of the invention〕

As explained above, according to the present invention, since the thin film transistor and its scanning line are formed of a low resistance film such as an amorphous silicon film, the pixel electrode can be formed overlappingly on the scanning line, so that the aperture ratio of the pixel can be increased. This has extremely excellent effects in that a display device that can be enlarged, has a bright screen, high resolution, and good image quality can be obtained.

[Brief explanation of drawings]

1 to 7 are diagrams illustrating an embodiment of a display device according to the present invention. 1...Pixel, 2...Thin film transistor (TFT)
), 3...substrate, 4...gate, 6...
Semiconductor, T...drain, 8...source, 9...
...Pixel electrode, 10...Video signal, 11...
・Color separation circuit, 12B, 12G. 12R...Life/analog memory, 30a...1 color pixel, 101.102,103...Scanning line, 2
01R. 201G, 201... signal line. Agent: Patent Attorney Katsuo Ogawa -1,X. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] It has a large number of pixels equipped with switching elements for display selection, these switching elements are connected to scanning lines and signal lines in a matrix, and the gate electrodes of the switching elements and the scanning lines are formed of an amorphous silicon film. A display device characterized by: