JPH0695144A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the picture element of the liquid crystal display element which lessens the fluctuation in the ratio of the capacity of a control capacitor electrode and accumulation capacity capacitor electrode arising from the variation in production process. CONSTITUTION:The picture element of this liquid crystal display element consists of a transparent substrate 1 which is formed with an insulating film 24 on its front surface, a second substrate 5 which is formed with a common electrode 6 on its rear surface, a liquid crystal 7 which is sealed between the common electrode 6 and the insulating film 24, plural auxiliary pixel electrodes 4, the control capacitor electrode 2, the accumulation capacity capacitor electrode 12 and a TFT 8 which controls the on and off of the picture elements. The above-mentioned control capacitor electrode 2 and the accumulation capacity capacitor electrode 12 are formed on the front or rear surface of the insulating film 24 which is the same surface common with each other and such control capacitor electrode 2 and accumulation capacity capacitor electrode 13 are respectively formed between the auxiliary pixel electrodes 4 disposed to face each other via the insulating film 24.

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 comprising a plurality of sub-pixels and capable of multi-gradation display.

[0002]

2. Description of the Related Art A prior art of a liquid crystal display element capable of multi-gradation display comprising a plurality of sub-pixels will be described with reference to FIG. FIG. 7A is a view showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 7B is a cross section taken along a line bb in FIG. 7A. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 7, reference numeral 1 denotes a transparent substrate made of, for example, transparent glass, a control capacitor electrode 2 is formed on the inner surface thereof, and an insulating film 15 is formed on the entire surface of the pixel on the upper surface of the control capacitor electrode 2. There is. This insulating film 15
A square sub-pixel electrode 4 ₁ is formed in the lower right corner of the upper surface, and a sub-pixel electrode 4 ₂ is formed over the entire surface of a substantially square pixel obtained by cutting a small square from the lower right corner of the square.
The source and drain of the TFT 8 are formed. The drain of the TFT 8 is formed in contact with the subpixel electrode 4 ₁ . An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel.
A storage capacitor electrode 12 is formed on the upper surface of the insulating film 24, and a gate electrode is formed at a position corresponding to the source and drain of the TFT 8.

The tip of the liquid crystal display device constructed as described above
In the row technology, first, the sub-pixel electrode 4 ₁And the common electrode 6
Liquid crystal capacitor C between_LC1Are formed, and the subpixel electrode 4 is formed.
₂And a liquid crystal capacitor C between the common electrode 6 and_LC3Formed
To be done. Sub-pixel electrode 4₁Four ₂And control capacitor electrode 2
And a control capacitor C_C2, C_C3Shape
Is made. In this prior art, as described above,
Pixel electrode 4₁And sub-pixel electrode 4₂L-shape formed between and
Control capacitor electrode 2 and common electrode via a gap
Capacitor C between 6 and_LC2Is formed. Control
It is said that the capacitor electrode 2 is equivalently a subpixel electrode.
Is to say. In addition, the storage capacitor electrode 12 and the sub
Pixel electrode 4₂Storage capacity C between_S3Is formed.

[0005]

[Problems to be Solved by the Invention]
The storage capacitor capacitor electrode 12 and the gate electrode are the same.
It is formed on one insulating layer 24. And the control console
The sensor electrode 2 is formed below the sub-pixel electrode 4, and
TFT8 is the sub-pixel electrode 4₁Also adopt the configuration to connect to
Of. That is, the sub-pixel electrode 4₁Is the thin film transistor 8
Directly connected to the drain of the_aIs applied
Be done. The equivalent circuit of the pixel shown in FIG.
Pole 4₁From the capacitor to the common electrode 6 sequentially
The trace will be as shown in FIG. This equivalent
In the circuit, the voltage Va applied to each subpixel electrode is
Subpixel electrode capacitance C_LCAnd storage capacity C_SSum and subpixel electrode capacity
Quantity C _LCControl capacitor, which is the capacity connected in series with
Quantity C_CIt is determined by the capacity ratio between and. Prior art mentioned above
In operation, the storage capacitor electrode 12 and the control capacitor are
Since the denser electrode 2 and the denser electrode 2 were formed on different insulating films,
Determined by these electrodes due to variations in fabrication process
The capacitance that is generated varies, and this capacitance ratio depends on the manufacturing of liquid crystal display elements.
It will fluctuate due to process variations. Obey
Therefore, due to the manufacturing process variation, each sub-pixel electrode 4
The voltage applied to V fluctuates.

This prior art also has two insulating films, an insulating film 15 and an insulating film 24, as shown in FIG. 7, which is not advantageous in the manufacturing process of the liquid crystal display element. So I want to reduce this. The present invention provides a liquid crystal display device that solves the above problems.

[0007]

A transparent substrate 1 having an insulating film 24 formed on its upper surface, a second substrate 5 having a common electrode 6 formed on its lower surface, and a space between the common electrode 6 and the insulating film 24. In the liquid crystal display element including the enclosed liquid crystal 7, the plurality of sub-pixel electrodes 4, the control capacitor electrode 2, the storage capacitor electrode 12, and the TFT 8 for controlling ON / OFF of the pixel, the control capacitor electrode 2 and the storage The capacitance capacitor electrode 12 is formed on the upper surface or the lower surface of the insulating film 24, which is the same common surface, and the control capacitor electrode 2 and the storage capacitor electrode 12 are opposed to each other via the insulating film 24. 4, a liquid crystal display element is formed which forms a control capacitor capacitance or a storage capacitance between the liquid crystal display device and the liquid crystal display device.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 1A is a view showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 1B is a cross section taken along a line bb in FIG. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 1, reference numeral 1 is a transparent substrate made of, for example, transparent glass. The control capacitor electrode 2, the source and drain of the TFT 8 and the storage capacitor capacitor electrode 12 are formed on the inner surface of the transparent substrate 1. The drain of the TFT 8 is formed in contact with the control capacitor electrode 2. An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. With this in the insulating film 24 top subpixel electrode 4 ₂ is formed, a gate electrode is formed at corresponding to the source and the drain of the TFT 8. A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof.
Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. A portion of the control capacitor electrode 2 which is not covered by the subpixel electrode 4 ₂ is equivalently equivalent to the first subpixel electrode 4
_Make up ₁ . The equivalent circuit of the first embodiment is as shown in FIG.

In this first embodiment, the storage capacitor electrode 12 and the control capacitor electrode 2 are formed on the same upper surface or lower surface of the insulating film 24 which is a common surface. By forming both electrodes on the same layer, even if variations occur in the manufacturing process of the liquid crystal display element, variations in the capacitance ratio of the storage capacitor and the capacitance ratio of the control capacitor are reduced. Since the control capacitor electrode 2 is formed by using the insulating film 24 as a dielectric, one insulating film 15 to be formed can be omitted as compared with the above-described prior art. Further, since the insulating film between the common electrode 6 formed subpixel electrodes 4 ₂ and its upper does not exist, there is no accumulation of problems charge at the interface between the insulating film and the alignment layer. Therefore, this liquid crystal display element also has an effect of suppressing the burn-in phenomenon. That is, when the liquid crystal display element displays a pattern by driving by applying a direct current, an afterimage of the immediately preceding pattern can be recognized when another pattern is displayed. The liquid crystal display element is driven by an alternating current in order to prevent an afterimage, but during this driving, charges are trapped in the insulating film and a direct current component is applied to the liquid crystal. Since this first embodiment the sub-pixel electrode 4 ₂ above the insulating film does not exist, the burn-in phenomenon is suppressed.

A second embodiment of the liquid crystal display element of the present invention will be described with reference to FIG. FIG. 2A is a view showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 2B is a sectional view taken along a line bb in FIG. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 2, reference numeral 1 is a transparent substrate made of, for example, transparent glass. The control capacitor electrode 2, the source and drain of the TFT 8 and the storage capacitor 12 are formed on the inner surface of the transparent substrate 1. The drain of the TFT 8 is formed in contact with the control capacitor electrode 2. An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. Sub-pixel electrodes 4 ₁ and 4 ₂ are formed on the upper surface of the insulating film 24, and gate electrodes are formed at positions corresponding to the source and drain of the TFT 8. In this case, prior to forming the sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 ₂ , an opening 15H reaching the control capacitor electrode 2 is formed in the insulating film 24 where the sub-pixel electrode 4 ₁ is formed later. The subpixel electrode 4 ₁ is formed so as to be in contact with the control capacitor electrode 2 when the subpixel electrode 4 ₁ is formed.
A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof. Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. In addition, L between the subpixel electrode 4 ₁ and the subpixel electrode 4 ₂ in the control capacitor electrode 2
The portion facing the letter-shaped gap equivalently constitutes a part of the _first subpixel electrode 4 ₁ . The equivalent circuit of the second embodiment is as shown in FIG.

In the second embodiment, the subpixel electrode 4 ₁ and the subpixel electrode 4 ₂ are formed on the upper surface of the insulating film 24 which is the same layer, and the subpixel electrode 4 ₁ and the control capacitor electrode 2 are opened. It is electrically connected through the hole 15H. In the second embodiment, a part of the control capacitor electrode 2, which is a polar plate for applying a voltage to the liquid crystal 7, the sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 are used.
_Since there is almost no insulating film above ₂ , the accumulation of charges at the interface between the insulating film and the alignment film is further suppressed as compared with the first embodiment. The storage capacitor electrode 12 and the control capacitor electrode 2 are formed on the same common surface, that is, at the interface between the transparent substrate 1 and the insulating film 24, and the control capacitor electrode 2 insulates the insulating film 24. The fact that it is formed as a body is the same as in the first embodiment. In addition, the subpixel electrode 4
Since ₁ and 4 ₂ and the insulating film between the common electrode 6 formed on the upper does not exist, there is no accumulation of problems charge at the interface between the insulating film and the alignment layer. Therefore,
This liquid crystal display element also has an effect of suppressing the burn-in phenomenon.

A third embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 3A is a view showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 3B is a cross section taken along a line bb in FIG. 3A. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 3, reference numeral 1 is a transparent substrate made of, for example, transparent glass. The control capacitor electrode 2, the source and drain of the TFT 8 and the storage capacitor 12 are formed on the inner surface of the transparent substrate 1. The drain of the TFT 8 is formed in contact with the control capacitor electrode 2. An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. The sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 are formed on the upper surface of the insulating film 24.
₂ is formed, and a gate electrode is formed at the location corresponding to the source and drain of the TFT 8. A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof. Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. The portion of the control capacitor electrode 2 facing the L-shaped gap between the subpixel electrode 4 ₁ and the subpixel electrode 4 ₂ equivalently constitutes a part of the _first subpixel electrode 4 _1. .

A third embodiment, the sub-pixel electrodes 4 ₁ and the control capacitor electrode 2 through the opening 15H in the second embodiment is omitted to be electrically connected, the sub-pixel electrodes 4 ₁
And forms a control capacitor C _C1 between the overlap of the control capacitor electrode 2 as the area about the same sub-pixel electrodes 4 ₁ and the sub-pixel electrode 4 ₁ and the control capacitor electrode 2 and the. The principle of operation is similar to that shown in FIG. 2, and the optical characteristics are similar to those shown in FIG. The equivalent circuit of the third embodiment is as shown in FIG.

A fourth embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 4A is a diagram showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 4B is a sectional view taken along a line bb in FIG. 4A. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 4, reference numeral 1 is a transparent substrate made of, for example, transparent glass. The sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 ₂ are formed on the inner surface of the transparent substrate 1, and
The source and drain of T8 are formed. The drain of the TFT 8 is formed in contact with the control capacitor electrode 2. An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. The control capacitor electrode 2 is formed on the upper surface of the insulating film 24, the storage capacitor electrode 12 is formed, and the gate electrode is formed at a position corresponding to the source and drain of the TFT 8. A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof.
Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. The control capacitor electrode 2 equivalently constitutes the subpixel electrode 43. The equivalent circuit of the fourth embodiment is as shown in FIG.

The fourth embodiment shown in FIG. 4 is one in which the control capacitor electrode 2 is formed above the sub-pixel electrode 4. Compared with the third embodiment shown in FIG. The positional relationship between 2 and the sub-pixel electrode 4 is vertically inverted. In this case, the storage capacitor electrode 12 can be formed simultaneously with the gate electrode. Since the low resistance material can be used for the gate electrode, the storage capacitor electrode bus can be formed with low resistance.

A fifth embodiment of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 5A is a view showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and FIG. 5B is a sectional view taken along a line bb in FIG. It is the figure seen in the arrow direction, and (c) is the figure which looked at the cross section which is shown by the straight line cc in (a) in the arrow direction.

In FIG. 5, reference numeral 1 is a transparent substrate made of, for example, transparent glass. The sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 ₂ are formed on the inner surface of the transparent substrate 1, and the source and drain of the TFT 8 are formed. The drain of the TFT 8 is formed in contact with the subpixel electrode 4 ₁ . An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. The control capacitor electrode 2 and the storage capacitor 12 are formed on the upper surface of the insulating film 24, and the gate electrode is formed at a position corresponding to the source and drain of the TFT 8. In this case, before the control capacitor electrode 2, the storage capacitor 12 and the gate electrode are formed, an opening 15H reaching the subpixel electrode 4 ₁ is formed where the control capacitor electrode 2 of the insulating film 24 is formed later. When the control capacitor electrode 2 is formed, the control capacitor electrode 2
Are formed in contact with the sub-pixel electrode 4 ₁ . A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof. Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. The equivalent circuit of the fifth embodiment is as shown in FIG.

The fifth embodiment shown in FIG. 5 is shown in FIG.
In the fourth embodiment, the control capacitor electrode 2 is
Elementary electrode 4₁Control capacitor capacity by forming contact with
Quantity C _C2Corresponds to the infinite. Control capacitor
Capacity C_C3It is possible to adopt a configuration that makes the
It Referring to FIG. 6, a sixth embodiment of the liquid crystal display device of the present invention is shown.
I will explain. FIG. 6A shows a plate-shaped liquid crystal display device.
It is a figure which shows the plane of one pixel cut out and shown vertically.
(B) is the same as the line bb in (a).
It is the figure which looked at the cross section of batter in the arrow direction, and (c) is in (a).
In the direction of the arrow in the section indicated by the straight line cc in
It is the figure seen.

In FIG. 6, reference numeral 1 is a transparent substrate made of, for example, transparent glass. A control capacitor electrode 2, a bottom gate electrode of the TFT 8 and a storage capacitor 12 are formed on the inner surface of the transparent substrate 1. An insulating film 24 is formed on the upper surfaces of these over the entire surface of the pixel. The sub-pixel electrode 4 ₁ and the sub-pixel electrode 4 ₂ are formed on the upper surface of the insulating film 24, and the source and drain of the TFT 8 are formed.
Here, the drain of the TFT 8 is formed in contact with the subpixel electrode 4 ₁ . A second transparent substrate 5 has a transparent common electrode 6 formed on the inner surface thereof. Then, the liquid crystal 7 is sealed between the common electrode 6 and the insulating film 24. In addition,
A portion of the control capacitor electrode 2 facing the L-shaped gap between the subpixel electrode 4 ₁ and the subpixel electrode 4 ₂ equivalently constitutes a part of the subpixel electrode 4 ₁ . The equivalent circuit of the sixth embodiment is as shown in FIG.

In the case of the sixth embodiment, the control capacitor electrode 2, the storage capacitor 12 and the bottom gate electrode can be simultaneously formed of the same material, which is convenient in the manufacturing process. In addition, since there is no insulating film between the sub-pixel electrodes 4 ₁ and 4 ₂ and the common electrode 6 formed thereabove, there arises a problem of charge accumulation at the interface between the insulating film and the alignment film. Absent. Therefore, this liquid crystal display element also has an effect of suppressing the burn-in phenomenon.

By the way, in the embodiments of the present invention shown in FIGS. 1 to 5, the TFT 8 has a top gate structure. However, the structure of the TFT 8 is not limited to this. When the top gate structure is adopted, either the stagger structure shown in FIG. 10A or the coplanar structure shown in FIG. 10B may be used. Also, when the bottom gate structure is adopted, either the reverse stagger structure shown in FIG. 10C or the reverse coplanar structure shown in FIG. 10D may be used. These T
Various techniques for realizing the FT structure have been developed, but these are not described in detail because they have no direct relation to the gist of the present invention.

[0026]

As described above, in the liquid crystal display device of the present invention, the control capacitor electrode 2 and the storage capacitor electrode 12 are the same common surface of the insulating film 24.
Forming on the upper surface or the lower surface reduces variations in the capacitance of the storage capacitor 12 and the capacitance ratio of the control capacitor electrode even if variations occur in the manufacturing process of the liquid crystal display element. As a result, the voltage applied to each sub-pixel electrode 4 is less likely to change due to variations in the manufacturing process. In addition, one layer of an insulating film to be formed as compared with the conventional example of the liquid crystal display element shown in FIG. 7 can be omitted.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first embodiment of a liquid crystal display element of the present invention, (a) is a diagram showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 2 is a diagram for explaining a second embodiment of the liquid crystal display element of the present invention, FIG. 2 (a) is a diagram showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 3 is a diagram for explaining a third embodiment of the liquid crystal display element of the present invention, (a) showing a plane of one pixel vertically cut out from the plate-shaped liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 4 is a view for explaining a fourth embodiment of the liquid crystal display element of the present invention, (a) showing a plane of one pixel vertically cut out from the plate-like liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 5 is a diagram illustrating a fifth embodiment of the liquid crystal display element of the present invention, FIG. 5A is a diagram showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 6 is a view for explaining a sixth embodiment of the liquid crystal display element of the present invention, (a) showing a plane of one pixel vertically cut out from the plate-like liquid crystal display element, (B) is a view of the cross section indicated by the straight line bb in (a), viewed in the direction of the arrow, and (c) is a cross section indicated by the straight line cc of the (a), viewed in the direction of the arrow. It is a figure.

FIG. 7 is a diagram illustrating a conventional example of a liquid crystal display element,
(A) is a diagram showing a plane of one pixel vertically cut out from a plate-shaped liquid crystal display element, and (b) is a sectional view taken along a line bb in (a) as seen in an arrow direction. Figure,
(C) is the figure which looked at the cross section shown by the straight line cc in (a) in the arrow direction.

FIG. 8 is an equivalent circuit of a liquid crystal display element.

FIG. 9 is another equivalent circuit of the liquid crystal display element.

10A and 10B are diagrams showing a TFT structure, FIG. 10A shows a staggered structure, FIG. 10B shows a coplanar structure, FIG. 10C shows an inverted staggered structure, and FIG. 10D shows an inverted coplanar structure. .

[Explanation of symbols]

1 Transparent Substrate 2 Control Capacitor Electrode 4 ₁ Sub-Pixel Electrode 4 ₂ Sub-Pixel Electrode 5 Second Substrate 6 Common Electrode 7 Liquid Crystal 8 TFT 12 Storage Capacitor Capacitor Electrode 24 Insulation Film

Claims (1)

[Claims] 1. A transparent substrate having an insulating film formed on its upper surface,
A second substrate having a common electrode formed on its lower surface, a liquid crystal enclosed between the common electrode and an insulating film, a plurality of subpixel electrodes, a control capacitor electrode, a storage capacitor electrode, and a pixel turned on. In a liquid crystal display element including a TFT for controlling OFF, a control capacitor electrode and a storage capacitor electrode are formed on the same common surface, that is, an upper surface or a lower surface of an insulating film. Is a liquid crystal display device characterized in that it forms a control capacitor capacity or a storage capacity with a sub-pixel electrode arranged oppositely via an insulating film.