JP2000010118A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: In a liquid crystal display device having a built-in drive circuit, when a light-shielding layer is formed in a drive circuit of a TFT substrate, an increase in TFT leak current is suppressed, light leakage is prevented, and Prevent cracking of the light shielding layer. A light-shielding film is formed on at least a portion other than a TFT portion and a wiring over a drive circuit portion of a TFT substrate having a display portion having a plurality of switching elements and a plurality of pixel electrodes, and a drive circuit portion for driving the display portion. I do.

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, and more particularly to a light-shielding film for a driving circuit of a liquid crystal display device with a built-in driving circuit.

[0002]

2. Description of the Related Art Liquid crystal display devices are lightweight, thin, and have low power consumption.
Alternatively, it has been widely applied to projection televisions, liquid crystal projectors, and the like. The performance that is always required for such displays is high image quality, and the number of companies that enter this field has intensified the market competition and demanded even lower costs. One technology that meets these requirements is a liquid crystal display device with a built-in drive circuit. That is, the driving circuit for the liquid crystal has been provided outside the display panel, but by incorporating this driving circuit, the cost is reduced and the image quality is improved. In order to incorporate this drive circuit, TFT
It is necessary to improve the performance of the TFT. One technique for improving the performance is a low-temperature polysilicon TFT.

Until now, what has been generally called a TFT uses amorphous silicon for a semiconductor layer. The amorphous silicon is irradiated with a laser to convert the silicon into polycrystal (polysilicon), and further, N-type and P-type ions are implanted into the semiconductor layer to form an N-channel TFT and a P-channel type. High performance switching devices for TFTs, low temperature polysilicon TFTs, have been developed. At present, small- and medium-sized liquid crystal displays have been commercialized as liquid crystal display devices incorporating a driving circuit using the low-temperature polysilicon TFT.

If this low-temperature polysilicon TFT technology is applied to a projection type liquid crystal display device such as a projection television or a liquid crystal projector for the purpose of low cost and high image quality, the problem of the projection type liquid crystal display device is raised. For example, there is light shielding in the drive circuit section. Because a powerful lamp of several hundred watts is used as the light source of the projector, strong light is incident on the liquid crystal panel, and when the strong light is irradiated on the polysilicon TFT, a photocurrent is generated.
This is because the off-characteristics are deteriorated and a malfunction occurs in the drive circuit. In addition, when a liquid crystal projector projects on a screen, there is a problem that it is very difficult to see if a bright portion is left around an area projected as an image. As a countermeasure against this, it can be easily inferred that light is shielded around the display section with the same structure as the pixel driving element.
Note that an example in which light is shielded by a pixel driving element is described in, for example,
No. 179108.

[0005]

However, if the entire driving circuit portion and the peripheral portion are simply covered with the light-shielding film, the light-shielding film is cracked due to the film stress of the light-shielding film, and light leaks from the crack. Or a short-circuit, or a bad influence on the film above and below the light-shielding film. Further, when the light-shielding film is formed of a conductor, there is a problem in that a capacitive load is formed by the wiring constituting the drive circuit and the light-shielding film, and the performance of the drive circuit is reduced.

Accordingly, an object of the present invention is to provide a liquid crystal display device having a built-in drive circuit. When a light-shielding layer is formed in a drive circuit of a TFT substrate, an increase in light leakage current of the TFT is suppressed, and light leakage is prevented. Another object of the present invention is to provide a liquid crystal display device that prevents cracks in a light-shielding layer and does not lower the performance of a driving circuit by a light-shielding film.

[0007]

An object of the present invention is to provide a display unit having a plurality of switching elements and a plurality of pixel electrodes, a TFT substrate having a drive circuit for driving the display unit, and a TF.
In a liquid crystal display device having a counter substrate facing a T substrate and a liquid crystal sealed between the TFT substrate and the counter substrate, at least a portion other than wiring and a TFT portion are provided on a drive circuit portion of the TFT substrate. This problem can be solved by providing a light-shielding film on the substrate and using a conductor that does not transmit light as a material of the wiring.

In the above structure, first, by providing a light-shielding film on the TFT portion, it is possible to suppress an increase in light leakage current of the TFT and to shield the TFT portion from light.
Next, by using a material that does not transmit light as the wiring material,
Wiring can be shielded from light. The drive circuit part is
Since it is composed of TFTs and wiring, the entire driving circuit is shielded from light by applying a light-shielding film to portions other than the wiring portion.

The reason why the light-shielding film is cracked is that when the film exists continuously over a wide area, the film itself contracts or expands due to the film stress. One way to solve the cracks is to not make the film continuous and wide. In the formation of the light-shielding film by the above method, since the light-shielding film is not applied to the wiring portion of the drive circuit portion, the light-shielding film is divided into small portions and arranged. That is, since the light shielding film is not continuously arranged in a wide area, it is possible to prevent the light shielding film from cracking.

Further, when a light-shielding film is provided on the entire surface of the drive circuit portion, the performance of the drive circuit deteriorates because a capacitive load is formed between the light-shielding film and the wiring, which increases the load. In the formation of the light-shielding film by the above method, the light-shielding film is not formed on the wiring, so that the capacitive load between the light-shielding film and the wiring is reduced, and the performance of the drive circuit can be maintained.

In the above liquid crystal display device, a light-shielding film is also formed on a part of the wiring, and the light-shielding films are all electrically connected to have the same potential. In other words, a stable driving circuit can be provided by fixing the light-shielding film, which has been divided into small portions, which is independent of potential and has an unstable potential to at least a certain potential. In addition, there is a problem that when a DC voltage is applied to the liquid crystal, the life of the liquid crystal is shortened. Therefore, by setting the potential applied to the light shielding film to the common potential of the liquid crystal, no potential is applied to the liquid crystal.
Long life of liquid crystal.

In the above liquid crystal display device, the light shielding film is chamfered. As a phenomenon that the light-shielding film is cracked, there are many things that occur from the corners of the light-shielding film. The cause of this phenomenon is that the film stress is concentrated at the corner. Therefore, by chamfering the light shielding film, it is possible to prevent the light shielding film from cracking. The chamfering is to make a right-angled corner such as 90 degrees into a 135-degree corner or round it on the mask pattern, or to make a 270-degree right-angled corner into a 225 degree corner or round it. .

Further, the above object is to provide a display unit having a plurality of switching elements and a plurality of pixel electrodes, a TFT substrate having a drive circuit for driving the display unit, an opposing substrate facing the TFT substrate, In a liquid crystal display device having a substrate and liquid crystal sealed between the opposed substrates, the periphery of the display portion and the drive circuit portion are covered with a peripheral electrode formed of the same material as the pixel electrode, and do not transmit light to the liquid crystal. It can also be solved by applying a potential. By applying a certain voltage to the liquid crystal, light is transmitted or not. By applying the light-impermeable voltage to the peripheral electrode, the periphery of the display portion and the driving circuit can be shielded by liquid crystal.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a drive circuit section of a TFT substrate constituting a liquid crystal display device of the present invention. FIG.
FIG. 2 is a plan view of FIG. FIG. 3 is a plan view schematically showing a TFT substrate constituting the liquid crystal display device of the present invention.

First, referring to FIG. 3, the TFT substrate 0
1 includes a display unit 20 and a drive circuit unit 30 on a transparent substrate 10 such as glass. Display unit 20
Is formed with a plurality of signal lines 21 and a plurality of scanning lines 22 so as to be orthogonal to the plurality of signal lines 21, and at each intersection of the signal lines 21 and the scanning lines 22, a pixel switching element 23 is connected to the pixel switching element. Pixel electrode 24.

The drive circuit section 30 includes a signal driver 31 having a shift register circuit and a sampling circuit for sending a signal to a signal line, and a scan driver 3 having a shift register circuit for sequentially selecting a scan line.
2 is constituted. These circuits are basically TFTs that are active elements,
It is composed of two components of wiring for supplying electric power to T and as a resistor.

FIG. 1 is a sectional view of a portion where a TFT portion 40 and a wiring portion 50 of a drive circuit portion exist. Transparent substrate 1
The TFT portion 40 and the wiring portion 50 are formed on the substrate 0, and the light-shielding film 60 according to the present invention is formed via the interlayer insulating film 51. The light shielding film 60 has at least
The portion other than the TFT portion 40 and the wiring portion 50 is covered. As shown in FIG. 2, the light-shielding film and the wiring portion are overlapped with a large margin in the accuracy of the alignment in consideration of the production deviation of the light-shielding film and the wiring layer.

FIG. 4 is a diagram showing a method of manufacturing a light shielding film. To a place where the wiring pattern and the TFT pattern are already arranged on the transparent substrate and the driving circuit is formed (FIG. 4A), an insulator such as silicon nitride is formed on the interlayer insulating film 51 by a method such as plasma CVD.
Is formed (FIG. 4b). Next, a light-shielding film 60 such as MoSi, which hardly transmits light, is formed as a thin film by, for example, a sputtering method (FIG. 4C). Next, the light-shielding film according to the present invention can be formed by patterning the light-shielding film by, for example, a photolithography method. However, in the display portion, it is necessary to make a through hole in the interlayer insulating film in the middle to electrically connect to the pixel electrode.

FIG. 5 is a schematic view of a liquid crystal projector using the liquid crystal display device of the present invention as an example. The light emitted from the light source 71 enters the condenser lens 72 and the like once.
The light is efficiently incident on the liquid crystal display device 80. The light that has passed through the liquid crystal display device is enlarged by the projection lens 73 and is projected on a screen 74. Here, the light source 71
Is emitted not only to the display section of the liquid crystal display device but also to the drive circuit section. However, since the light-shielding film is also provided on the drive circuit, malfunction of the drive circuit can be prevented.

[0021]

According to the liquid crystal display device of the present invention, in a driving circuit built-in type, the driving circuit portion is shielded from light by a light shielding film, and
Part of the wiring portion is not shielded from light, so that only the display portion can be projected on the screen, and a malfunction of the TFT, which is a switching device constituting the drive circuit, is prevented, and the capacitance between the light-shielding film and the wiring is reduced. The load can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating a light-shielding portion of a liquid crystal display device driving circuit of the present invention.

FIG. 2 is a plan view showing the plane of FIG. 1;

FIG. 3 is a diagram schematically showing a liquid crystal display device of the present invention.

FIG. 4 is a side sectional view showing a method for manufacturing a liquid crystal display device drive circuit partial light-shielding film of the present invention.

FIG. 5 is a configuration diagram schematically showing a projection type liquid crystal display device using the liquid crystal display device of the present invention.

[Explanation of symbols]

01: TFT substrate, 10: transparent substrate, 20: display unit, 2
DESCRIPTION OF SYMBOLS 1 ... Signal line, 22 ... Scan line, 23 ... Pixel switching element, 24 ... Pixel electrode, 30 ... Drive circuit part, 31 ... Signal driver, 32 ... Scan driver, 40 ... TFT part, 5
0: wiring portion, 51: interlayer insulating film, 60: light shielding film, 71
... Light source, 72 ... Condenser lens, 73 ... Projection lens, 74 ...
Screen, 80: Liquid crystal display device.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Genro Kawachi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi, Ltd. F-term (reference) 2H091 FA34Y FD04 GA13 LA03 LA11 MA07 2H092 GA59 JA24 JB51 KB25 MA05 MA08 NA15 NA16 NA22 NA23 PA06 PA09 RA05 2H093 NA16 NC34 ND19 ND42 ND54 NE06 NG02 5C006 BB16 BC20 EB05 EC11 FA33 5C094 AA31 AA53 BA03 BA43 CA19 DA09 ED15 FB12 HA10

Claims (4)

[Claims] A display unit having a plurality of switching elements and a plurality of pixel electrodes; a TFT substrate having a drive circuit for driving the display unit; a counter substrate facing the TFT substrate;
In a liquid crystal display device having a TFT substrate and liquid crystal sealed between the counter substrate, a film which does not transmit light is used for wiring of the driving circuit, and at least a portion other than the wiring is formed on the driving circuit portion of the TFT substrate. And a liquid crystal display device having a light shielding film in a TFT portion. 2. A liquid crystal display device according to claim 1, wherein all of said light-shielding films are electrically connected and have the same potential. 3. The liquid crystal display device according to claim 1, wherein all of the light-shielding films are electrically connected and have a common potential with respect to the liquid crystal. 4. A liquid crystal display device according to claim 1, wherein said light shielding film is chamfered.