JPH04182629A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease the level shift of an impressed voltage and to allow high-grade displaying by providing isolated electrodes in such a manner that signal electrodes and picture element electrodes form storage capacitors via insulating layers. CONSTITUTION:The 1st storage capacitors 101, 103 are formed of the signal electrodes 15a, b and the isolated electrodes 31a, b via the insulating layers and the 2nd storage capacitors 102, 104 connected in series to the 1st storage capacitors are formed of the electrodes 31a, b and the picture element electrodes 19 via the insulating layers. The level shift of an impressed voltage, i.e. DELTAVp, is sufficiently lowered by providing the storage capacitors connected in parallel with a liquid crystal capacitor Clc in such a manner. The storage capacitors are constituted by the series connection of the 1st storage capacitors and the 2nd storage capacitors, by which the impression of a constant voltage to the picture element electrodes 19 by the other storage capacitors is obviated even if a pinhole, etc., arise in the insulating films constituting at least either of the storage capacitors.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an active matrix liquid crystal display device in which each pixel is provided with a switching element, and particularly to its structure.

(Prior Art) In recent years, liquid crystal display devices have come into widespread use in various fields, taking advantage of their light weight and low power consumption.

Among these, active matrix liquid crystal display devices, in which a switching element is provided for each pixel, are capable of high contrast display with little crosstalk.
It is attracting particular attention.

A specific structure of an active matrix type liquid crystal display device is, for example, a liquid crystal composition is sandwiched between a pair of electrodes. A plurality of signal electrodes and scanning electrodes are formed in a matrix on one electrode substrate, and a thin film transistor connected to a pixel electrode is installed as a switching element at each intersection. Furthermore, a counter electrode facing the pixel electrode is formed on the other electrode substrate.

By the way, in each display pixel of such an active matrix type liquid crystal display device, the gate and
Since a parasitic capacitance Cgs exists between the source electrodes, when the gate voltage applied from the scanning electrode to the gate electrode switches from ON to OFF, the signal voltage applied to the pixel electrode shifts to the negative side by ΔVp. .

This ΔVp can be logically determined by the following equation (1), and if ΔVp is large, the screen may flicker, making it impossible to ensure high display quality.

ΔVp = (Vg, on-Vg, off) * Cg
s/ (Cgs+ Clc) - (1) Vg, On; Gate-on voltage Cgs; Gate-source capacitance Vg, off'; Gate-off voltage C1c; Liquid crystal capacitance Therefore, for example, a storage capacitor C is formed in parallel with the liquid crystal capacitor C1c. This is how ΔVp is reduced.

As a specific structure, a storage capacitor C is formed by forming a storage capacitor electrode to which a predetermined voltage is applied so as to overlap the pixel electrode via an insulating layer.

(Problems to be Solved by the Invention) In order to reduce ΔVp of a liquid crystal display device by providing a storage capacitor electrode, high reliability of the insulating layer is required. This is because if a defect such as a pinhole exists in the insulating layer, the storage capacitor electrode and the pixel electrode will be short-circuited, and the voltage of the storage capacitor electrode will always be applied to the liquid crystal composition, causing display defects.

In order to solve the above-mentioned problems, for example, Japanese Patent Laid-Open No. 1-239531 describes a liquid crystal display device in which a plurality of storage capacitors C are connected in series. With this redundant design in which multiple storage capacitors C are connected in series, even if one storage capacitor C shorts out due to a pinhole in the insulating layer, other storage capacitors C will connect the storage capacitor electrode and the pixel electrode. Since there is no electrical connection,
Good display can be performed.

However, sequentially providing a first storage capacitor electrode that overlaps with the pixel electrode through an insulating layer and a second storage capacitor electrode that overlaps with the first storage capacitor electrode through an insulating layer requires a significant increase in the manufacturing process. This was not desirable as it led to an increase in

The present invention has been made in view of the above-mentioned problems, and enables high-quality display by sufficiently reducing the level shift of the applied voltage of a liquid crystal display device, that is, ΔVp, and also enables high manufacturing yield and high productivity. The object of the present invention is to provide an active matrix type liquid crystal display device that can obtain the following characteristics.

[Structure of the Invention] (Means for Solving the Problems) The active matrix liquid crystal display device of the present invention has a plurality of signal electrodes and scanning electrodes arranged in a matrix, and intersections between the signal electrodes and the scanning electrodes. a first electrode substrate having a thin film transistor connected to the pixel electrode; a second electrode substrate having a counter electrode facing the pixel electrode; and a second electrode substrate sandwiched between the first electrode substrate and the second electrode substrate. an active matrix type liquid crystal display device, comprising a signal electrode, a pixel electrode, and an isolated electrode disposed such that a storage capacitor is formed through an insulating layer. It is something.

(Function) As described above, the active matrix type liquid crystal display device of the present invention is provided with isolated electrodes so that a storage capacitor is formed through the signal electrode, the pixel electrode, and the insulating layer.

With such a configuration, the first storage capacitor is formed by the signal electrode and the isolated electrode via the insulating layer,
Further, a second storage capacitor is formed which is connected in series to the first storage capacitor by the isolated electrode and the pixel electrode via the insulating layer.

By providing a storage capacitor connected in parallel with the liquid crystal capacitor C1c in this way, the level shift of the applied voltage, that is, Δ
Vp can be sufficiently reduced.

By configuring the storage capacitor by connecting the first storage capacitor and the second storage capacitor in series, even if a pinhole or the like occurs in the insulating film that constitutes at least one storage capacitor, the other storage capacitor A constant voltage is not applied to the pixel electrode.

Furthermore, by configuring a plurality of storage capacitors by providing an isolated electrode so as to overlap the signal electrode and the pixel electrode through the insulating layer, the storage capacitor electrode can be provided so as to overlap the pixel electrode through the insulating layer. It can be manufactured using the same manufacturing process as conventional liquid crystal display devices.

(Example) Hereinafter, an active matrix liquid crystal display device (1) according to an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic front view of the active matrix liquid crystal display device (1) of this embodiment, and FIG. 2 shows a schematic cross-sectional view taken along line AA' in FIG. 1. .

The active matrix liquid crystal display device (1) includes a first
A liquid crystal composition (61) is sandwiched between an electrode substrate (11) and a second electrode substrate (51).

The first electrode substrate (11) is an insulating glass substrate (13)
A plurality of signal electrodes (15) and scanning electrodes (17) are formed in a matrix on the top. A thin film transistor (21) connected to the pixel electrode (19) is located at each intersection of the signal electrode (15) and the scanning electrode (17).
is installed.

To explain this thin film transistor (21) in detail, a gate electrode (21a) formed integrally with a scanning electrode (17) is installed on an insulating glass substrate (13),
Silicon oxide (SiOX) is placed on this gate electrode (2ia).
) is provided. and,
On the gate electrode (21a) via this insulating layer (23), i-type hydrogenated amorphous silicon is deposited on the semiconductor layer (23).
5), and furthermore, n-type hydrogenated amorphous silicon electrically isolated from each other is formed on the semiconductor layer (25) as a drain region (27) and a source region (29).
It is formed as. This drain region (27) is connected to a signal electrode (15) by a drain electrode (21b) in which a molybdenum (MO) film and an aluminum (A1) film are laminated.
Similarly, the source region (29) is also made of molybdenum (Mo
) film and an aluminum (AI) film are stacked to form a source electrode (2Lc) connected to the pixel electrode (19).

In addition, in the active matrix liquid crystal display device (1) of this example, each pixel electrode (19) and each pixel electrode (
19) Two signal electrodes (15a) installed adjacent to
, (15b) and two isolated electrodes (31a) and (31b) are respectively formed so as to overlap with the insulating layer (23).

On the thus formed first electrode substrate (11), a low-temperature cure type polyimide resin for aligning the liquid crystal composition (61) in a predetermined direction is rubbed in a predetermined direction, and an alignment film (35 ).

Further, the second electrode substrate (51) is connected to the first electrode substrate (1
1. on an insulating glass substrate (53) similar to 1). T.

0.0 (Indium Tin Oxide) is installed as a common electrode (55), and a light shielding layer (57) made of aluminum formed in a matrix is installed on this common electrode (55). This light shielding layer (57) is
This is provided for the purpose of preventing malfunction due to irradiation of light to the thin film transistor (21) formed on the first electrode substrate (11).

Also on the thus formed second electrode substrate (51), a low-temperature cure type polyimide resin for aligning the liquid crystal composition (61) in a predetermined direction is rubbed in a predetermined direction to form an alignment film (58). It is set up as.

A liquid crystal composition (61) is sandwiched between the first electrode substrate (11) and the second electrode substrate (55) at a predetermined interval.

Furthermore, a first electrode substrate (11) and a second electrode substrate (51)
), polarizing plates (39) and (59) are installed in alignment with each other, thereby configuring the active matrix type liquid crystal display device (1) of this embodiment.

Active matrix liquid crystal display device (1) of this example
) has the above-described configuration, so each pixel has an equivalent circuit as shown in FIG.

That is, one signal electrode (19) adjacent to one pixel electrode (19)
There is a signal electrode (15a) between the pixel electrode (19) and the pixel electrode (19).
5a) - Insulating layer (23) - First storage capacitor C1 (101) formed by first isolated electrode (31a), first isolated electrode (31a) - Insulating layer (23) one pixel electrode (
19) and the second storage capacitor C2(10
2) are connected in series.

Also, between the other signal electrode (15b) and the pixel electrode (19), the signal electrode (15b) - the insulating layer (23) - the second
A third storage capacitor C3 (103) formed by the isolated electrode (31b), and a fourth storage capacitor C3 (103) formed by the second isolated electrode (31b)-insulating layer (23) one pixel electrode (19) This means that the capacitor C4 (104) is connected in series.

Therefore, simply the insulating layer (23) between the signal electrodes (15a), (L5b) and the isolated electrodes (31a), (31b)
) Even if a pinhole etc. occurs in the isolated electrode (31a)
, (31b) - Storage capacitance C2 (102) formed by the insulating layer (23) and one pixel electrode (19).

Since C4 (104) is formed, the pixel electrode (19
) is never applied with a signal voltage.

This also applies when pinholes etc. occur in the insulating layer (23) between the isolated electrodes (31a), (31b) and the pixel electrode (19), and pinholes etc. in the insulating layer (23) occur. Display defects caused by this can be significantly reduced, and manufacturing yield can be improved.

Furthermore, in the active matrix liquid crystal display device (1) of this embodiment, the storage capacitances CI (101) and C2 (
102), C3 (103), C4 (104
), the parasitic capacitance Cg formed between the gate electrode (121a) and the source electrode (121c) is reduced.
s turns the voltage applied to the scanning electrode (107) ON.
It is possible to reduce the level shift that occurs when switching from to OFF. As a result, an active matrix liquid crystal display device (1) capable of high-quality display could be obtained.

In addition, in the active matrix liquid crystal display device (1) of this embodiment, one signal electrode (15a) adjacent to one pixel electrode (19) and one pixel electrode (19) are arranged as described above.
) and the first isolated electrode (31a) provided so as to overlap with each other via the insulating layer (23), one pixel electrode (19)
The other signal electrode (15b) and pixel electrode (15b) adjacent to
The second isolated electrode (31, b) was provided so as to overlap with the second isolated electrode (31, b) via the insulating layer (23). In combination with such a configuration, adjacent signal electrodes (15a)
, (15b) by inverting the polarity of the signal voltage applied to each line, for example, to drive the storage capacitors C1 (101) and C2 (102).

C3 (103) and C4 (104) are signal electrodes (1
It was possible to prevent the display from being adversely affected by the polarity of 5a) and (15b).

Furthermore, according to the structure of the active matrix liquid crystal display device (1) of this embodiment, for example, thin film transistors (2
Storage capacitors C1 (101), C2 (102), C3 are formed in the same process as forming the gate electrode (21a) in 1).
(103), an isolated electrode (31a) forming C4 (104).

The active matrix type liquid crystal display device M(1) can be manufactured by the same steps as the conventional method except for manufacturing (31b). Therefore, the active matrix liquid crystal display device (1) of this embodiment can significantly reduce the manufacturing process compared to a device in which a plurality of storage capacitor electrodes and insulating layers are stacked and storage capacitors are connected in series.

In addition, the isolated electrodes (31a) and (31b) are connected to 1.
T.O.

Even if it is considered that a plurality of storage capacitor electrodes and insulating layers are formed, it is not necessary to laminate a plurality of storage capacitor electrodes and insulating layers (and the productivity will not be significantly reduced).

[Effects of the Invention] As detailed above, according to the liquid crystal display device of the present invention,
By providing isolated electrodes that overlap the signal electrode and the pixel electrode via the insulating layer, a plurality of storage capacitors are formed by series connection using at least one insulating layer.

Therefore, a configuration in which a plurality of storage capacitors are connected in series can be achieved without significantly increasing the manufacturing process.

Furthermore, by connecting a plurality of storage capacitors in series, display defects will not occur even if pinholes or the like occur in the insulating layer forming one of the storage capacitors.

Therefore, manufacturing yield can be improved and pixel defects can be prevented for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of an active matrix type liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of the active matrix type liquid crystal display device in FIG. 1 taken along line AA'. , FIG. 3 shows an equivalent circuit diagram of one display pixel of the active matrix type liquid crystal display device shown in FIG. (1) ≧ Active matrix liquid crystal display device (15
)...Signal electrode (17)...Scanning electrode (1
9)...Pixel electrode (21)...Thin film transistor (23)...Insulating layer (31a), (31b)...Isolated electrode (61)...
・Liquid crystal composition (101), (102), (103), (
104)...Storage Capacity Agent Patent Attorney Nori Chika
Yudo Takehana Kikuo fl 77 live maen, 7 prongs 1 run, 1 da 1 1st figure 1 [ 3rd figure

Claims (1)

[Scope of Claims] A first electrode substrate including a plurality of signal electrodes and scanning electrodes arranged in a matrix, and a thin film transistor connected to a pixel electrode at an intersection of the signal electrode and the scanning electrode; , a second electrode comprising a counter electrode facing the pixel electrode.
an active matrix liquid crystal display device comprising: an electrode substrate; and a liquid crystal layer sandwiched between the first electrode substrate and the second electrode substrate; 1. An active matrix liquid crystal display device comprising isolated electrodes arranged so as to form a storage capacitor.