JPH05150269A - Thin film transistor panel - Google Patents

Abstract

(57) [Summary] [Object] To provide a TFT panel in which a capacitor line is provided so as to face a pixel electrode, and the aperture width of a pixel electrode portion can be increased to increase the aperture ratio of a liquid crystal display element. To do. [Structure] At least a portion of the capacitor line facing the pixel electrode 2 is a transparent film made of a transparent conductive film 21.

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 panel used for an active matrix liquid crystal display device.

[0002]

2. Description of the Related Art A thin film transistor panel (hereinafter referred to as a TFT panel) used for an active matrix liquid crystal display device has the following structure. 5 and 6 show a conventional TFT panel, FIG. 5 is a partial sectional view, and FIG. 6 is a plan view.

In this TFT panel, a large number of pixel electrodes 2 and a large number of thin film transistors (TFTs) 3 which are active elements thereof are formed on a transparent substrate 1 made of glass or the like. Generally, it has an inverted stagger structure.

This thin film transistor 3 having an inverted stagger structure
Is a gate electrode G formed on the substrate 1, a gate insulating film 4 covering the gate electrode G, and an i-type semiconductor layer 5 formed on the gate insulating film 4 so as to face the gate electrode G. , The source electrode S and the drain electrode D formed on the i-type semiconductor layer 5 via the n-type semiconductor layer 6, and the n-type semiconductor layer 6 is the i-type semiconductor layer 5.
Are separated in a portion corresponding to the channel region (region between the source electrode S and the drain electrode D) of.

The gate electrode G is integrally formed with a gate line GL formed on the substrate 1, and the gate line GL and the gate electrode G are formed of a metal such as Al or Al alloy, Cr, Ta. ing. The gate insulating film 4 is formed of Si N (silicon nitride) or the like, the i-type semiconductor layer 5 is formed of a-Si (amorphous silicon), and the n-type semiconductor layer 6 is doped with n-type impurities. -Si.

In the figure, 7 is the i-type semiconductor layer 4
Is a blocking layer made of Si 3 N or the like formed on the channel region of the n-type semiconductor layer 6 formed on the i-type semiconductor layer 5 in manufacturing the thin film transistor 3. It is provided to prevent the channel region of the i-type semiconductor layer 5 from being etched when the corresponding portion is separated by etching.

Further, the gate insulating film 4 of the thin film transistor 3 is formed on almost the entire surface of the substrate 1 so as to cover the gate line GL, and the pixel electrode 2 and the data line DL are provided with the gate insulating film (transparent film) 4 Is formed on.

The data line DL is formed integrally with the drain electrode D of the thin film transistor 3, and the data line DL, the drain electrode D and the source electrode S are made of Al or a metal such as Al alloy, Cr and Ta. Has been formed.

The pixel electrode 2 is formed of a transparent conductive film made of ITO or the like, and the pixel electrode 2 is formed by overlapping one end of the pixel electrode 2 on the source electrode S of the thin film transistor 3. , Is connected to the source electrode S.

Although not shown, the thin film transistor 3 and the data line DL are formed on the surface of the TFT panel.
A protective insulating film (SiN film or the like) is formed to cover the surface, and the surface is subjected to orientation treatment.

As shown in FIG. 5, the active matrix liquid crystal display element is constructed by arranging the TFT panel and the counter panel 10 so as to face each other and enclosing the liquid crystal between both panels.

The counter panel 10 is formed by forming a transparent counter electrode 12 on the transparent substrate 11 so as to face each pixel electrode 2 of the TFT panel. The surface of the counter panel 10 is also subjected to orientation treatment. It

Further, on the substrate 11 of the counter panel 10, a black mask 13 for blocking the transmitted light of a portion other than the pixel display area corresponding to each of the pixel electrodes 2 has a grid pattern (see FIG. 6). ) Is formed. The black mask 13 is formed of a metal film such as Cr, and the counter electrode 12 is formed on a transparent insulating film (SiN film or the like) 14 that covers the black mask 13.

By the way, in the active matrix liquid crystal display element, in order to reduce the fluctuation of the potential held in the pixel electrode during the non-selection period, the TFT panel is provided with a storage capacitor corresponding to each pixel electrode 2. It is provided.

In FIGS. 4 and 5, CL is a capacitor line for forming the above-mentioned storage capacitor, and the capacitor line CL is formed of the same metal as the gate line GL on the substrate 1.

The capacitor line CL is composed of a line portion along the gate line GL and a projecting portion extending from one side of the line portion so as to correspond to each pixel electrode 2. The side edge portion and each protruding portion face one side edge portion and one end edge portion of the pixel electrode 2 via the gate insulating film 4.

The storage capacitor is composed of the capacitor line CL, the pixel electrode 2 and the gate insulating film 4 between them, and this storage capacitor is used when the pixel electrode 4 is selected (when the thin film transistor 3 is turned on).
The electric charge applied to the pixel electrode 2 is accumulated and the potential of the pixel electrode during the non-selection period is held. The capacitor line CL is connected to a reference potential (for example, ground potential) at a terminal portion (not shown).

[0018]

However, in the conventional TFT panel described above, the capacitor line CL is made of the same metal as the gate line GL (Al or Al alloy, Cr,
Since the gate line GL and the capacitor line CL can be simultaneously formed at the time of manufacturing the TFT panel since it is formed of Ta, etc., on the other hand, on the other hand, the opening width of the pixel electrode portion (width of the region through which light is transmitted). ) There was a problem that W was regulated by the capacitor line CL.

Since the capacitor line CL is a metal film, the light transmitted through the pixel electrode portion is transmitted through the capacitor line CL.
Therefore, the opening width W of the pixel electrode portion becomes smaller than the width of the pixel electrode 2 by the overlap amount of the capacitor line CL. As shown in FIGS. 5 and 6, in the TFT panel in which one side edge of the line portion of the capacitor line CL and each protrusion are opposed to one side edge and one edge of the pixel electrode 2, The vertical and horizontal opening widths of the electrode portions are both reduced.

The opening width W'of the black mask 13 provided on the counter panel 10 of the liquid crystal display element is formed to be slightly smaller than the opening width W of the pixel electrode portion of the TFT panel as shown in FIGS. Since the opening width W ′ of the black mask 13 becomes the width of the display pixel, the liquid crystal display element using the above conventional TFT panel has a small opening ratio, and the brightness and the contrast are lowered. Had the problem of doing

The present invention provides a TFT panel in which a capacitor line is provided so as to face a pixel electrode, but the aperture width of a pixel electrode portion can be increased to increase the aperture ratio of a liquid crystal display element. It is intended for.

[0022]

According to the present invention, a pixel electrode, a thin film transistor which is an active element thereof, and a capacitor line which forms a storage capacitor line between the pixel electrode and the pixel electrode are provided on a transparent substrate. In the TFT panel, at least a portion of the capacitor line facing the pixel electrode is a transparent film made of a transparent conductive film.

[0023]

According to the TFT panel of the present invention, since at least the portion of the capacitor line facing the pixel electrode is formed of a transparent film, the transmitted light of the pixel electrode portion is not blocked by the capacitor line, and therefore the capacitor line is used. There is no reduction in the opening width of the pixel electrode portion.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a part of the TFT panel, and FIG. 2 is a plan view of the TFT panel. 1 and 2, the conventional TF shown in FIGS. 5 and 6 is used.
Components corresponding to the T panel are denoted by the same reference numerals, and description of components having the same configuration as the conventional TFT panel is omitted.

In the TFT panel of this embodiment, of the gate line GL and the capacitor line CL formed on the substrate 1, the gate line GL is Al or Al alloy, Cr,
The capacitor line CL is formed by a metal film made of Ta or the like.
Is a transparent conductive film 21 made of ITO or the like,
Other configurations are the same as those of the conventional TFT panel shown in FIGS.

This TFT panel is prepared by first substituting on the substrate 1.
It is conventionally performed after forming a capacitor line CL by forming a transparent conductive film and patterning the transparent conductive film, and then forming a gate line GL and a gate electrode G on the substrate 1 by forming a metal film and patterning the metal film. The thin film transistor 3 and the data line D are formed by a known method.
It is manufactured by a manufacturing method of forming L and the pixel electrode 2.

Then, in the TFT panel of this embodiment,
Since the capacitor line CL is a transparent film made of the transparent conductive film 21, the light transmitted through the pixel electrode portion is not blocked by the capacitor line CL.
According to the FT panel, light is transmitted through the entire area of the pixel electrode 2, so that the opening width W of the pixel electrode portion can be increased.

Therefore, if a liquid crystal display element is constructed by using this TFT panel, the opening width W'of the black mask 13 provided on the counter panel 10 can be increased, so that the aperture ratio of the liquid crystal display element is increased. It can be increased to improve brightness and contrast.

In the above embodiment, the gate line GL is used.
Although the gate line GL is formed of a metal film, the gate line GL may be formed of the same transparent conductive film as the capacitor line CL. In this case, the gate line GL and the capacitor line CL can be formed simultaneously. it can.

However, in this case, since the gate electrode G formed integrally with the gate line GL is also a transparent film, T
When light enters the FT panel from the lower surface side, a photocurrent flows through the i-type semiconductor layer 5 and the thin film transistor 3 malfunctions. Therefore, the gate line GL and the gate electrode G
A liquid crystal display element using a TFT panel formed of a transparent conductive film is preferably used under the condition that light does not enter the TFT panel from its lower surface side.

Further, in the above embodiment, the capacitor line CL is formed only by the transparent conductive film 21, but the capacitor line CL may be a transparent film at least in the portion facing the pixel electrode 2.

3 and 4 show another embodiment of the present invention. In this embodiment, the portion of the capacitor line CL facing the pixel electrode 2 is a transparent film of only the transparent conductive film 21, and the other portion of the capacitor line CL is Al or Al alloy on the transparent conductive film 21. The metal film 22 made of Cr, Ta, or the like is laminated to form a two-layer film, and the gate line GL and the gate electrode G are also formed to have the metal film 22 laminated on the transparent conductive film 21. The metal film 22 of the gate line GL and the gate electrode G
Are formed in the same pattern as the transparent conductive film 21 thereunder.

As in this embodiment, the capacitor line C
If the portion of the L that does not face the pixel electrode 2 is a two-layer film in which the metal film 22 is laminated on the transparent conductive film 21, the resistance value of the capacitor line CL can be lowered, and thus the capacitor line CL is arranged along the capacitor line CL. The charge / discharge characteristics of each storage capacitor corresponding to each pixel electrode 2 can be made substantially uniform.

That is, the charge / discharge characteristic of the storage capacitor formed between the capacitor line CL and the pixel electrode 2 is determined by the capacitor line CL between the storage capacitor and the reference potential connection terminal (terminal portion of the capacitor line CL). However, if the resistance value of the capacitor line CL is small, the difference in charge / discharge characteristics between the storage capacitor close to the reference potential connection end and the storage capacitor far from the reference potential connection end is small. The charge / discharge characteristics of each storage capacitor are almost uniform.

If the charge / discharge characteristics of each storage capacitor are substantially uniform, the potential of each pixel electrode 2 is also substantially uniform, so that the display characteristics of each pixel of the liquid crystal display element are made uniform and there is no display unevenness. A high quality image can be displayed.

Moreover, in this embodiment, the gate line G
Since the L and the gate electrode G are also two-layer films in which the metal film 22 is laminated on the transparent conductive film 21, even if light is incident on the TFT panel from the lower surface side, the light is transmitted to the metal film 2
2, so that the i-type semiconductor layer 5 can be shielded.
There is no possibility that a thin film transistor 3 malfunctions due to a photocurrent flowing therethrough. Further, since the gate line GL and the gate electrode G are the same two-layer film as the capacitor line CL, the gate line GL and the gate electrode G and the capacitor line CL can be simultaneously formed.

[0037]

In the TFT panel of the present invention, since at least the portion of the capacitor line facing the pixel electrode is a transparent film made of a transparent conductive film, the capacitor line is provided facing the pixel electrode. However, the aperture width of the pixel electrode portion can be increased, and thus the use of this TFT panel can increase the aperture ratio of the liquid crystal display element.

[Brief description of drawings]

FIG. 1 is a sectional view of a part of a TFT panel showing an embodiment of the present invention.

FIG. 2 is a plan view of the TFT panel.

FIG. 3 is a sectional view of a part of a TFT panel showing another embodiment of the present invention.

FIG. 4 is a plan view of the gate line and the capacitor line of FIG.

FIG. 5 is a partial cross-sectional view of a conventional TFT panel.

FIG. 6 is a plan view of the TFT panel.

[Explanation of symbols]

1 ... Substrate, 2 ... Pixel electrode, 3 ... Thin film transistor, GL
... gate line, G ... gate electrode, 4 ... gate insulating film,
5 ... i-type semiconductor layer, 6 ... n-type semiconductor layer, S ... Source electrode, D ... Drain electrode, DL ... Data line, CL capacitor line, 21 ... Transparent conductive film, 22 ... Metal film.

Claims (1)

[Claims] 1. A thin film transistor panel comprising a transparent substrate, a pixel electrode, a thin film transistor which is an active element thereof, and a capacitor line which forms a storage capacitor line between the pixel electrode and the pixel electrode. A thin film transistor panel, wherein at least a portion facing the pixel electrode is a transparent film made of a transparent conductive film.