JPS63292114A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain high transmittivity and a high contrast ratio, and also, to allow a display picture electrode to have a high performance so as not to generate a flicker, by providing a second display picture element electrode connected to a display picture element electrode formed on a first substrate, on the latter. CONSTITUTION:On the first substrate 31 on which a thin film transistor having a semiconductor film 34 between a drain 39 and a source electrode 40, and a display picture element electrode 38 are arrayed, and formed like a matrix, so as to oppose a gate electrode 32 provided on an insulating substrate, the second display picture element electrode 45 is formed so as to be superposed on a signal line and the gate electrode 32. Also, in a gap of the first substrate and the second display picture element electrode 45, a light shielding electrode 43 is formed so as to be superposed on the second display picture element electrode 45. In such a way, comparing with a conventional device, the numerical aperture becomes larger, therefore, high transmittivity is obtained, and also, since the light shielding electrode and the second display picture element electrode are superposed, a high contrast ratio, and a picture plane being free from a flicker can be obtained.

Description

[Detailed Description of the Invention] [Object of the Invention (Field of Industrial Application) The present invention is based on vii! The present invention is applied to an active matrix type liquid crystal display device using a transistor (hereinafter referred to as TPT) as an active element.

(Prior Art) In recent years, as a liquid crystal display device, active matrix type liquid crystal display devices with large capacity and high density are being actively developed and put into practical use for use in television displays, graphic displays, and the like. In such liquid crystal display devices, active elements are used as means for driving and controlling each pixel so that high contrast display without crosstalk can be performed.

MOSFETs formed on single-crystal Sl substrates have been used as active elements, but in recent years, MOSFETs formed on transparent insulating substrates have been used because they enable transmissive display and are easy to increase in area. TPT is used.

FIG. 7 is a cross-sectional view showing the structure of an accu-dip matrix type liquid crystal display device equipped with such a TPT array.
A gate electrode 2 integrated with a gate line is formed on a first substrate 1 made of glass or plastic, and is covered with an insulating layer. 13 is formed. And this insulation! At a predetermined position on f13 is a semiconductor made of, for example, hydrogenated amorphous silicon! 4 is formed, and a drain electrode 5 integrated with the signal line is formed so as to sandwich this semiconductor R4, for example, I To (Indiun Tin Oxid).
A display pixel electrode 6 consisting of e) and a source electrode 7 integrated with the display pixel electrode 6 are formed. Moreover, the semiconductor Jl! excluding this display pixel electrode 6! 4, drain electrode 5, and source electrode 7, an inorganic protective film 8 such as a silicon nitride film is formed, and an organic protective film 9 such as polyimide is formed on this inorganic protective film 8. There is. Then, on the organic protection WA9, there is a light shielding electrode 10, an organic protection 1!
[11 and a liquid crystal alignment film 12 are formed in sequence.

On the other hand, a color filter 14, a transparent counter electrode 15, and a liquid crystal alignment film 16 are formed in this order on the inner surface of a second substrate 13 made of glass or plastic and placed opposite to the first substrate 1.

The second substrate 13 and the first substrate 1 are sealed at their peripheries with a gap of about 10 μm maintained, and a liquid crystal 17 is sealed in the gap.

(Problems to be Solved by the Invention) However, in the conventional liquid crystal display device described above, T F
1' exists, so the display pixel 1N! There is a limit to increasing the area of 6, and there is a problem in that it is very difficult to obtain high transmittance and high contrast ratio.

The present invention has been made in order to solve the above-mentioned problems, and is an active matrix type display pixel electrode with high performance, high transmittance, high contrast ratio, and no flicker. The purpose of the present invention is to provide a liquid crystal display device.

[Configuration of the Invention (Amniotic Membrane for Solving Problems) The active matrix liquid crystal display device of the present invention has a drive circuit for each pixel including a display pixel electrode and a thin film semiconductor element in a lattice pattern on the main surface. a first substrate on which gate electrodes and source electrodes or drain electrodes are arranged in rows and columns and are wired vertically and horizontally to connect thin film semiconductor elements in rows and columns, respectively; and a first substrate facing the first substrate. an active matrix type liquid crystal display device comprising: a second substrate having a transparent counter electrode formed on its main surface; and a liquid crystal sandwiched between the first substrate and the second substrate; The present invention is characterized in that a second display pixel electrode connected to the display pixel electrode is formed on the display pixel electrode formed on the substrate.

(Function) The present invention is directed to a first substrate on which a thin film transistor having a semiconductor layer between a drain and a source electrode and a display pixel electrode are arranged in a matrix, facing a gate electrode provided on an insulating substrate. , by forming the second display pixel electrode so as to overlap the signal line and the gate electrode,
The display pixel area can be greatly expanded and high transmittance can be obtained.

Furthermore, since there is no unresponsive portion in the light transmission region, a high contrast ratio can be obtained.

Furthermore, by forming a light shielding electrode in the gap between the first substrate and the second display pixel electrode so as to overlap with the second display pixel electrode, the parasitic capacitance can be substantially reduced.
Flicker can be eliminated.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an equivalent circuit of an active matrix liquid crystal display device according to an embodiment, and shows a plurality of games) 11YJ (
J=1, 2, 3. ...-n> and the signal line X1 (i=1.
2.3. . . . m) A thin film transistor 21 is formed at each intersection position of 6. 22 in FIG. LCD 2 between
4 is being held.

FIG. 2 is a diagram showing a more detailed structure of the embodiment.

The illustration of the liquid crystal and the second substrate having a transparent counter electrode on the color filter and the color filter is omitted.

That is, a gate electrode 32 is formed on a second substrate 31 made of glass or plastic, and an insulating layer 33 such as a silicon nitride film is formed on this gate electrode 32.
is deposited, and further, for example, hydrogenated amorphous silicon or the like is deposited to form the semiconductor layer 34.

A heavily doped layer 135 made of a-3i doped with phosphorus or arsenic is formed on this semiconductor scrap 34, and the source electrode side and the drain electrode side are separated by etching to form an N-channel transistor. It is formed.

For example, ITO 36 and molybdenum 37 are sequentially deposited on the insulating layer 33 including the semiconductor R 34 and the n-type intermediate layer 35, and are etched into a predetermined shape to form a display pixel electrode 38. Then, for example, aluminum is deposited on the insulation R33 including the display pixel electrode 38 and the semiconductor R34, and further etched to form a drain electrode integrated with the signal line YJ with the semiconductor layer 34 in between. @3
9 and a source electrode 4° integral with the display pixel electrode 38 are formed.

Furthermore, the drain voltage tf439 and the display pixel electrode 38
On the source electrode 40, an inorganic protective film 41 such as a silicon nitride film and an organic protective film 42 such as polyimide are formed.
The inorganic protective film 41 on the 0 display pixel electrode 38, on which the 0 display pixel electrodes are sequentially deposited, is removed by etching.

Further, a light shielding electrode 43 is formed on the organic protection 141 to face the semiconductor scrap 34 and the n-type intermediate layer 35, and an organic protective film 44 is further formed on the organic protective film 42 and the light shielding electrode 43, A second display pixel electrode 45 is formed on the organic protective film 44 and the display pixel electrode 38, and a liquid crystal alignment film 46 is formed on the second display pixel electrode 45 and the organic protective film 44.

The first substrate 31 on which the liquid crystal alignment film 46 is formed in this way
, a second substrate on which a transparent counter electrode (not shown) is formed is placed opposite to the second substrate with a predetermined gap maintained and the peripheral portion sealed, and a liquid crystal 47 is sealed in the gap. There is.

In the active matrix liquid crystal display device configured in this way, as shown in FIGS. 3 and 4,
The second display pixel electrode 45 and the light shielding electrode 43 are formed to overlap.

Now, the driving operation in this active matrix type liquid crystal display device will be explained with reference to FIGS. 5 and 6.

Figure 5(a) shows the timing waveform of the gate pulse at the fifth
Figure (b) shows the signal pulse timing waveform, and Figure 5 (c) shows the signal pulse timing waveform.
5(d) shows the waveform of the light-shielding electrode, and FIG. 5(d) shows the waveform of the transparent counter electrode.

And gate voltage on time (t = 63.5 μsec
Although a signal voltage is written to the display pixel electrode 38, the potential of the display pixel electrode 38 changes after the gate voltage is turned off because a parasitic capacitance exists between the gate electrode and the display pixel electrode 38. This is Δv1 shown in FIG. Further, since the capacitance of the liquid crystal 47 corresponding to a given signal voltage differs, the potential change of the display pixel electrode 38 differs depending on the signal voltage.

As a result, in the conventional example, Fig. 6(C), Fig. 6(d), (
As shown in Δ■1≠ΔV2), the center value of the display pixel potential in the positive cycle and the negative cycle was not determined to be a constant voltage for any signal voltage.

On the other hand, as shown in FIG. 6 (a> and (b)), the display pixel potential in the positive cycle and negative cycle in this example is such that the change in potential of the display pixel electrode 38 is small, and (Δv
1ΦΔVl) The center value of the display pixel potential is determined to be a constant potential. Therefore, flicker can be completely eliminated.

[Effects of the Invention] As explained above, according to the active matrix liquid crystal display device of the present invention, the aperture ratio is larger than that of the conventional device, resulting in high transmittance. By overlapping them, a screen with a high contrast ratio and no flicker can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an equivalent circuit of an active matrix liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view showing the structure of the embodiment, and the third country shows the first pixel electrode in the embodiment. and a configuration diagram showing the second display pixel electrode, the fourth
The figure is a partial cross-sectional view of the example, Figure 5 is the gate voltage pulse waveform in the example, the signal voltage is a pulse waveform, the light shielding voltage waveform and the counter electrode voltage waveform, and Figure 6 is the conventional display pixel potential and the example. FIG. 7 is a cross-sectional view showing a conventional active matrix type liquid crystal display device. 21...Thin film transistor 22...
...Display pixel electrode 23...Transparent counter electrode 24...Liquid crystal 31...First substrate 32... ......Gate electrode 33...Insulating layer 34...Semiconductor layer 35...N middle layer

Claims (2)

[Claims] (1) Driving circuits for each pixel, each consisting of a display pixel electrode and a thin film semiconductor element, are arranged in a grid pattern on the main surface, and are wired vertically and horizontally to connect each thin film semiconductor element in rows and columns, respectively. a first substrate on which a gate electrode and a source or drain electrode are formed; a second substrate facing the first substrate and having a transparent counter electrode formed on its main surface; and the first substrate. In an active matrix liquid crystal display device comprising a liquid crystal sandwiched between second substrates, a second display pixel electrode is formed on the display pixel electrode formed on the first substrate and connected thereto. An active matrix liquid crystal display device characterized by: (2) The second display pixel electrode is formed so as to cover at least a part of the light shielding electrode disposed corresponding to the semiconductor layer. Active matrix type liquid crystal display device.