JPH0869009A - Tft type liquid crystal display device - Google Patents

Abstract

PURPOSE: To improve an opening rate and the brightness of display by forming source wirings and gate wirings respectively of opaque wiring parts and transparent wiring parts broader than these parts. CONSTITUTION: The source wirings and gate wirings are respectively formed of the opaque wiring parts 2, 4 and the transparent wiring parts 3, 5 broader than these parts. As a result, the broader source wiring parts 3 and transparent gate wiring parts 5 function as wirings for signal power sources as well in addition to the opaque source wiring parts 2 and the opaque gate wiring parts 4. The regions formed with the transparent source and gate wiring parts as part of the wirings are utilizable as a display region. Since the opaque source and gate wiring parts as light shielding regions are formable finer than the conventional wirings, the ratio of the display region to the area of the entire display screen, i.e., opening rate, is greatly improved without bringing the increase of wiring resistance.

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 type liquid crystal display device having an improved aperture ratio.

[0002]

2. Description of the Related Art A TFT type liquid crystal display device has recently attracted a great deal of attention due to its high image quality and the fact that it can be mass-produced by using a planar technique widely used for manufacturing semiconductors. This type of TFT type liquid crystal display device generally has a plurality of pixel electrodes arranged in a matrix for controlling the arrangement direction of liquid crystal molecules housed between glass substrates, and selectively controls these pixel electrodes. Thin film transistor (TF) provided corresponding to each pixel electrode for
T) and.

FIG. 4A shows a main part of a conventional TFT type liquid crystal display device. As shown in the figure, the conventional TFT type liquid crystal display device comprises a pixel electrode 21 as a display region and a TFT 22 provided corresponding to these pixel electrodes 21. The TFT 22 has a source electrode 24 electrically connected to the source wiring 23, a drain electrode 25 electrically connected to the pixel electrode 21, and a gate electrode 27 electrically connected to the gate wiring 26. are doing.

FIG. 4B shows a cross section taken along the line YY in FIG. 4A. As shown in the figure, the TFT 22 has an insulating film 29 on a gate electrode 27 formed on a glass substrate 28.
And the amorphous silicon (a
-Si) is formed on the semiconductor layer 31, and a conductive metal such as Al is deposited on the semiconductor layer 31 to form the source electrode 24.
And a drain electrode 25 are formed. Here, the drain electrode 25 is the pixel electrode 21 formed on the insulating film 30.
The source electrode 24 and the gate electrode 27 are electrically connected to the source wiring 23 and the gate wiring 26, respectively. With such a configuration, by applying a required voltage signal to the source line 23 and the gate line 26, each TFT 22 is selectively operated and the potential on the pixel electrode 21 connected to the drain electrode 25 of the TFT is changed. The liquid crystal held between the glass substrates is driven by controlling.

In the above-mentioned conventional liquid crystal display device, the area in which the pixel electrode 21 is formed is used as a display area for liquid crystal display, but the other area, that is, the TFT.
The area in which 22 is formed and the area between the pixel electrodes 21 in which the source wiring 23 and the gate wiring 26 are formed are non-display areas. Although not shown here, the display area on the inner surface of the other glass substrate facing the TFT 22 and the pixel electrode 21 is a light shielding area by forming a light shielding film made of Cr or the like.

[0006]

In the conventional TFT type liquid crystal display device, as described above, the source wiring 23 and the gate wiring 26 are provided between the pixel electrodes 21 arranged in a matrix.
Is formed, and not only the region where the TFT 22 is formed,
Since the area between the pixel electrodes 21 where the source wiring 23 and the gate wiring 26 are formed is also a non-display area, the ratio of the display area to the entire display screen of the TFT liquid crystal display device, that is, the aperture ratio, is at most 40. However, it is not possible to obtain a sufficiently bright display as the entire display screen. Particularly, in the TFT type liquid crystal display device, as described above, the TFTs 22 are line-sequentially scanned through the source wirings 23 and the gate wirings 26 formed in a grid pattern between a large number of pixel electrodes 21 arranged in a matrix. Since the voltage is selectively driven by
Even if an attempt is made to improve the aperture ratio by thinning the source wiring 23 and the gate wiring 26, if these wirings are thinned to a certain degree or more, the wiring resistance of the source wiring 23 and the gate wiring 26 excessively increases. As a result, the control signal is delayed and the screen display performance is degraded.

The present invention has been made in view of the above problems, and an object thereof is to provide a TFT type liquid crystal display device having an improved aperture ratio and an improved display brightness.

[0008]

To achieve the above object, according to the present invention, one of the glass substrates provided facing each other, the liquid crystal housed between the glass substrates, and one of the glass substrates is provided. A gate line formed on the surface, a source line formed orthogonally to the gate line, a TFT electrically connected to the gate line and the source line, and the TF
A TFT type liquid crystal display device comprising a pixel electrode electrically connected to T for driving the liquid crystal, wherein a source wiring and a gate wiring each include an opaque wiring portion and a transparent wiring portion wider than the opaque wiring portion. TFT characterized by
Type liquid crystal display device is provided.

The pixel electrode can be formed in an area on the substrate which extends over the transparent metal wiring portion adjacent to the gate wiring and over the transparent metal wiring portion adjacent to the source wiring.

[0010]

[Operation and effect] Since the source wiring and the gate wiring of the TFT type liquid crystal display device are respectively formed of the opaque wiring portion and the transparent wiring portion wider than the opaque wiring portion, the wide wiring is provided in addition to the opaque source wiring portion and the opaque gate wiring portion. The transparent source wiring portion and the transparent gate wiring portion also function as wiring for signal current. Therefore, the area where the transparent source and gate wiring portions are formed as a part of the wiring can be used as the display area, and the opaque source and gate wiring portions as the light shielding area can be made thinner than the conventional wiring. The ratio of the display area to the area of the entire display screen, that is, the aperture ratio can be significantly improved without increasing the wiring resistance.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a TFT type liquid crystal display device according to the present invention will be described in detail with reference to the drawings according to embodiments. Although not shown, the TFT type liquid crystal display device according to the present embodiment has a plurality of glass substrates arranged in a matrix for driving the liquid crystal on one inner surface of a glass substrate arranged to face each other through the liquid crystal. Pixel electrodes and T provided corresponding to each pixel electrode for controlling the voltage of these pixel electrodes
Have an FT. On the other glass substrate, a color filter is formed in a region corresponding to the pixel electrode, that is, a display region, and a light shielding film made of Cr or the like is formed in a region corresponding to between the TFT and the pixel electrode, that is, a light shielding region. Has been formed.

FIG. 1 shows the main part of the TFT type liquid crystal display device of this embodiment. Specifically, a source wiring, a gate wiring, a pixel electrode and the like formed on the inner surface of a glass substrate on which TFTs are formed. The positional relationship in planar view of is shown. Here, the source wiring and the gate wiring are respectively composed of an opaque wiring portion made of an opaque metal and a transparent wiring portion made of a transparent metal, as will be described later. FIG. 2 shows a cross section taken along line XX in FIG.

On the glass substrate 1, as shown best in FIG. 1, a plurality of opaque source wiring portions 2 are formed in strips in parallel with each other. Opaque source wiring part 2
As the material metal of Al, Al is used as a metal material that has a low electric resistance value and also matches the purpose of light shielding. A wide transparent source wiring portion 3 is formed on these opaque source wiring portions so as to cover them in the extending direction. As a material metal of the transparent source wiring portion 3, ITO having high light transmittance and conductivity is used.
(Indium tin oxide) is used. These laminated opaque and transparent source wiring portions 2 and 3 cooperate to form a source wiring.

On the transparent source wiring portion 3, a plurality of strip-shaped opaque gate wiring portions 4 are further opaque, with a wiring interlayer insulating film 13 made of SiOx which is entirely formed so as to cover them. The transparent source wiring portions 2 and 3 are formed in parallel with each other so as to be orthogonal to each other.
As the material metal of the opaque gate wiring portion 4, Al is used as in the opaque source wiring portion 2. A wide transparent gate wiring portion 5 is formed on these opaque gate wiring portions 4 so as to cover them in the direction in which they extend.
Are formed. As the material metal of the transparent gate wiring portion 5, ITO (indium tin oxide) is used as in the transparent source wiring portion 3. These stacked opaque and transparent gate wiring portions 4 and 5 cooperate to form a gate wiring.

A TFT 6 to be described later is provided in the vicinity of each intersection of the opaque source wiring portion 2 and the opaque gate wiring portion 4. An electric field is selectively formed on the transparent gate wiring portion 5 through a pixel electrode lower insulating film 14 made of SiOx so as to cover the transparent gate wiring portion 5 and driving liquid crystal molecules made of ITO. The pixel electrode 7 for forming the pixel is formed so as to correspond to the TFT 6 and define a unit pixel.

Each TFT 6 is a so-called stagger type in which the gate electrode is provided on the side opposite to the substrate, amorphous silicon (a-Si) (not shown) is used as the semiconductor film, and it is opaque as shown in an enlarged view in FIG. A source electrode 8 made of Al electrically connected to the source wiring portion 2;
The drain electrode 9 also made of Al and electrically connected to the corresponding pixel electrode 7 and facing the source electrode 8, and the source and drain electrodes 8 and 9 electrically connected to the opaque gate wiring portion 4. Al provided between
And a gate electrode 10 composed of. In the figure, the transparent source wiring portion and the transparent gate wiring portion are omitted for easy understanding. Here, the connection between the source electrode 8 and the opaque source wiring portion 2 is made through the transparent source wiring portion 3, the insulating film, and the contact holes 11 provided in the opaque and transparent gate wiring portions 4 and 5. Further, the connection between the gate electrode 10 and the opaque gate wiring portion 4 is made via the transparent gate wiring portion 5 and the contact hole 12 provided in the wiring interlayer insulating film 13.

Next, a method of manufacturing the TFT type liquid crystal display device of this embodiment will be described. An Al film was formed on one surface of a glass substrate used for the TFT type liquid crystal display device of this embodiment by vapor deposition to have a film thickness of about 10,000 angstroms.
20μ by patterning by etching
To form a plurality of opaque source wiring portions 2 parallel to each other. After forming the opaque source wiring portions, an ITO film is formed by sputtering to have a thickness of about 3000 angstroms so as to cover them, and patterning is performed by etching to form a strip-shaped transparent source wiring portion 3 having a wiring width of 100 μ by about 10 μm. Are formed at the wiring intervals.

Next, a SiOx film is formed by plasma CVD so as to cover the transparent source wiring portion 3 at a temperature of about 300 ° C. to a thickness of about 5000 Å, and is then etched into a desired pattern to form the wiring interlayer insulating film 13. Form. After the wiring interlayer insulating film 13 is formed, an Al film is formed thereon by evaporation to a thickness of about 10000 angstroms, and patterning is performed by etching to form 20 μm wide parallel and opaque or transparent source wiring portions 2, A plurality of opaque gate wiring portions 4 orthogonal to 3 are formed. After forming the opaque gate wiring portions 4, an ITO film is formed by sputtering to a thickness of about 3000 angstroms so as to cover them, and patterning is performed by etching to form a strip-shaped transparent gate wiring portion 5 having a wiring width of 100 μ. It is formed with a wiring interval of 10 μ.

Next, a SiOx film is formed by plasma CVD so as to cover the transparent gate wiring portion 5 at a temperature of about 300 ° C. to a film thickness of about 5000 angstroms, and is then etched into a desired pattern to form an insulating film 14 under the pixel electrode.
Then, an ITO film is formed by sputtering to a film thickness of about 3000 angstroms, and then etching is performed to form pixel electrodes 7 in the respective regions defined by the opaque source wiring portion 2 and the opaque gate wiring portion 4.

Each TFT is formed in the same step as the above wiring and the like. That is, the source electrode 8 of each TFT is the opaque source wiring portion 2, the gate electrode 10 is the opaque gate wiring portion 4, and the drain electrode 9 is the corresponding pixel electrode 7.
They are formed so as to be electrically connected to each other. Instead of such a connection, the source electrode 8 may be connected to the transparent source wiring portion 3 and the gate electrode 10 may be connected to the transparent gate wiring portion 5. In this case, n is connected to each connection interface.
It is preferable to form a + type amorphous silicon (a-Si) layer.

In the liquid crystal display device of this embodiment, when used, the source wiring, that is, the opaque and transparent source wirings 2 and 3, and the gate wiring, that is, the opaque and transparent gates, are provided below the pixel electrode for controlling the molecular alignment of the liquid crystal. Although the signal voltage is supplied via the wirings 4 and 5, an electric field shielding film made of ITO as a conductor is provided between the transparent gate wiring 5 and the pixel electrode 7 via an insulating film of SiOx. , For example,
If the liquid crystal molecules are configured to be held at the ground potential, it is possible to effectively prevent an unnecessary electric field from being applied to the liquid crystal molecules by the voltage applied to the source wirings 2 and 3 and the gate wirings 4 and 5, so that a more appropriate liquid crystal display can be obtained. can get.

Although Al is used for the opaque source and gate wiring portions 2 and 4 in the above-mentioned embodiments, the present invention is not limited to this, and instead of Al, the electrical resistance is low and the light is shielded. Other metals that fit the purpose, such as Cr and T
It is possible to use a, etc.

[Brief description of drawings]

FIG. 1 is a partially enlarged plan view showing a main part of a substrate of a TFT type liquid crystal display device of the present invention.

2 is a cross-sectional view of the substrate of FIG. 1 taken along lines XX and YY.

FIG. 3 is an enlarged plan view of a TFT on the substrate of FIG. 1 and its vicinity.

FIG. 4 is a partially enlarged plan view showing a main part of a substrate of a conventional TFT type liquid crystal display device, and a sectional view of a TFT.

[Explanation of symbols]

 1 substrate 2 opaque source wiring portion 3 transparent source wiring portion 4 opaque gate wiring portion 5 transparent gate wiring portion 6 TFT 7 pixel electrode 8 source electrode 9 drain electrode 10 gate electrode

Front page continuation (72) Inventor Makoto Takamura 21, Saizo-mizozaki-cho, Ukyo-ku, Kyoto City Rome Stock Company

Claims (2)

[Claims] 1. A glass substrate provided facing each other,
The liquid crystal housed between the glass substrates, the gate wiring formed on one inner surface of the glass substrate, the source wiring formed orthogonal to the gate wiring, and the gate wiring and the source wiring electrically connected to each other. Connected to the TFT and the TF
A TFT type liquid crystal display device comprising a pixel electrode electrically connected to T for driving the liquid crystal, wherein the source wiring and the gate wiring each include an opaque wiring portion and a transparent wiring portion wider than the opaque wiring portion. A TFT type liquid crystal display device characterized by the above. 2. The TFT according to claim 1, wherein the pixel electrode is formed in a region on the substrate that straddles an adjacent transparent metal wiring portion of the gate wiring and straddles an adjacent transparent metal wiring portion of the source wiring. Type liquid crystal display device.