JPH03103830A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the voltage fluctuation of a pixel electrode caused by the variation of a signal voltage on a source wiring and the variation of a signal voltage on a data bus line by forming the source wiring, and a low dielectric constant insulating layer on a gap between the pixel electrode and the source wiring. CONSTITUTION:On a transparent insulating substrate 1 on which a pixel electrode 3 and a source wiring 4 are formed, SiO2 being a low dielectric constant insulating material is allowed to film and a low dielectric constant insulating film 12 is generated, a resist pattern 11 is formed thereon, and thereafter, by peeling off the resist pattern 11, a low dielectric constant insulating layer 6 is formed. In this state, the coupling capacity of the gap between the source wiring 4 and the pixel electrode 3 is small, the potential of the pixel electrode 3 is scarcely influenced by a signal voltage on the source wiring 4, and the display of a further multi-gradation can be executed. In such a manner, the voltage fluctuation of the pixel electrode caused by capacity coupling can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix liquid crystal display device (hereinafter abbreviated as AM-LCD) used for liquid crystal displays and the like.

[Prior Art] In recent years, high-definition display elements containing a large amount of image information have been actively developed. In the area of one pixel, a pixel electrode, an active device CM film transistor (TPT), a two-terminal element (
AM-LCDs in which diodes such as MIM, Hallisters, etc.) are formed need to reduce the area of both the pixel electrode and the active device when achieving higher definition. However, miniaturization of active devices has limits in terms of device characteristics. Furthermore, in order to obtain a bright display screen, it is necessary to increase the aperture ratio, and in order to increase the area of the pixel electrode, the gap between the pixel electrode and the wiring is narrowed.

As a result, capacitive coupling between the pixel electrode and the wiring using the liquid crystal layer as a dielectric layer increases, and the potential of the pixel electrode when not selected changes depending on the influence of the signal voltage on the source wiring. In other words, when performing gradation display depending on the voltage, the voltage step width must be larger than the voltage fluctuation width.
Floor 1+1' Display ability decreases. Therefore, in order to perform high gradation display, it is necessary to study a structure that can suppress voltage fluctuations of pixel electrodes.

Below, among AM-LCDs, thin film transistor type liquid crystal display devices (hereinafter abbreviated as TPT-LCDs) and
A two-terminal element type liquid crystal display device (hereinafter abbreviated as two-terminal-LCD) will be described.

FIG. 6(a) is a diagram showing the structure of a conventional TPT-LCD, and FIG. 6(b) is a sectional view taken along line AA' in FIG. 6(a). In the figure, 1 is a transparent insulating substrate, 2 is a thin film transistor, 3 is a pixel electrode, 4 is a source wiring, and 5 is a gate wiring. As shown in the figure, the conventional TPT matrix array has a structure in which source wiring 4 and pixel electrode 3 are arranged close to each other.

Similarly, FIG. 7(a) is a diagram showing the structure of a conventional two-terminal LCD, and FIG. 7(b) is a diagram showing the structure of A-A in FIG. 7(a).
It is a sectional view along the line. In the figure, 1 is a transparent insulating substrate;
10 is a two-terminal element, 3 is a pixel electrode, and 9 is a data bus line. As shown in the figure, it has a structure in which the conventional 2b::1 element 71, the top of the RIX array, the data hash twin 9, and the pixel electrode 3 are arranged close to each other.

Therefore, for T P T - L C D,
The above-mentioned capacitances C and D are generated in the gap between the source wiring 4 and the pixel electrode 3 using the liquid crystal layer as a dielectric layer. Also, 2-terminal LCD
Regarding this, the above-mentioned capacity I C s n occurs in the gap between the data bus line 9 and the pixel electrode 3 in which the liquid crystal layer is a dielectric layer. The source wiring vA4 and the pixel electrode 3 and the data bus line 9 and the pixel electrode 3 are coupled in an alternating current capacitive manner via the capacitor CSD, and the voltage of the unselected pixel electrode 3 is applied to the source wiring 4 and the data bus line 9. Easily fluctuates due to the influence of changes in the image signal voltage. Therefore, depending on the magnitude of the voltage, in the normal method of displaying gradations, it is necessary to make the step width of the voltage larger than the voltage fluctuation width, making it difficult to express many gradations.

[Problem to be solved by the invention]

As mentioned above, in the conventional AM-LCD structure, the capacitance C■ of the gap between the pixel electrode 3 and the source line 4 and the pixel electrode 3
The capacitance CSO of the gap between the data bus line 9 and the data bus line 9 increases as the number of pixels increases and the higher the resolution of the AM-LCD becomes. The problem is that it is easily affected by changes in the signal voltage on the bus line.
It is difficult to produce an AM-LCD capable of high-definition, multi-gradation display.

An object of the present invention is to reduce the capacitance of the gap between the pixel electrode and the source wiring, and between the data bus line and the pixel electrode, and to prevent voltage fluctuations of the pixel electrode due to changes in the signal voltage on the source wiring or signal voltage on the data bus line. The goal is to prevent

4 [Means for Solving the Problems] In the present invention, thin film transistors 2 and pixel electrodes 3 are arranged in a matrix array on a transparent insulating substrate l, and source wirings 4 are arranged in the column direction of the pixel electrodes, and source wirings 4 are arranged in the row direction of the pixel electrodes. In a liquid crystal display device in which a gate wiring 5 is disposed on the substrate and a liquid crystal layer 8 is sandwiched between the transparent insulating substrate 1 and the opposite transparent electrode substrate 7, a low M
An active matrix type liquid crystal display device having a structure in which a t-rate insulating layer is formed, and a two-terminal element (M
IM (diodes, varistors, etc.) 10 and pixel electrodes 3
are arranged in a matrix array, data bus lines 9 are arranged in the column direction of the pixel electrodes, and the transparent insulating substrate 1
In a liquid crystal display device in which a liquid crystal layer 8 is sandwiched between a transparent electrode substrate 7 and a facing transparent electrode substrate 7, an active matrix type liquid crystal display device has a structure in which a low dielectric constant insulating layer 6 is formed on the gap between the data bus line 9, the pixel electrode, and the data bus line. This is an active matrix liquid crystal display device characterized in that the product display device and the low dielectric constant insulating layer 6 serve as spacers for maintaining the cell gap of the liquid crystal display device.

[Effect]

By forming the low dielectric constant insulating layer 6, liquid crystal having a high dielectric constant can be removed from between the pixel electrodes and the source electrodes, and between the pixel electrodes and the data bus lines.

If SiO2 is used as the material for the low dielectric constant insulating layer 6, the relative dielectric constant is about 4. On the other hand, the dielectric constant of liquid crystal is l
It is about 0 to 15, which is about 3 times as much. Therefore, by replacing the liquid crystal with a material having a low dielectric constant, the capacitance between the pixel 3 and the source line 4 and the capacitance between the pixel 3 and the data bus line 9 are reduced to about 173 before the replacement. Therefore, the voltage of the pixel electrode 3 is less susceptible to the influence of the source line voltage and the data bus line voltage, and voltage fluctuations are reduced. In other words, it becomes possible to control the voltage for gradation display in smaller voltage increments. Therefore, it has become possible to display images with multiple gradations.

[Example 1] Figure 1 below (El). (11) and Fig. 3 Ol)
An embodiment of the TFT-LCD of the present invention will be described from to (C) D along with its manufacturing process.

On the transparent insulating substrate 1 (FIG. 3(a)) on which the pixel electrode 3 and the source wiring 4 are formed, Si0, which is a low dielectric constant insulating material, is deposited.
2 was deposited to a thickness of 4 μm by plasma CVD to form a low dielectric constant insulating film 12 (FIG. 3(b)). Subsequently, a resist pattern II was formed on the SiOz (Fig. 3 (Cl)), and then the substrate was dry etched by RIE using CF gas (Fig. 3 (d)), and then the resist was peeled off. Then, a low dielectric constant insulating layer 6 was formed (FIG. 3(e)). Thereafter, liquid crystal was injected between the transparent insulating substrate 1 and the counter transparent electrode substrate 7 to form a TP with a liquid crystal cell gap of 5 μm.
A T-LCD was produced.

The TPT matrix array obtained as above is (
(see Figures 1(a) and (b)), the coupling capacitance between the source wiring and the pixel electrode is small, and the potential of the pixel electrode is almost unaffected by the signal voltage on the source wiring. It is now possible to display.

[Example 2] Below, Fig. 2 (a), (b) and Fig. 4 (a) - (
In accordance with d), one embodiment of the two-terminal LCD of the present invention will be described together with its manufacturing process.

On the transparent insulating substrate 1 (FIG. 4(a)) on which the pixel electrodes 3 and data bus lines 9 are formed, photosensitive polyimide (Photonys, manufactured by Toray), which is a low dielectric constant insulating material, is spin-coated to a thickness of 3 μm. A low dielectric constant insulating film 12 was formed (FIG. 4(b)). After pre-hake, the pattern of the low dielectric constant insulating layer 6 is exposed through the mask 13 (FIG. 4(C))
L. Thereafter, a low dielectric constant insulating layer 6 was formed by performing development and post-hake (FIG. 4(d)). Thereafter, liquid crystal was injected between the transparent insulating substrate 1 and the opposing transparent electrode substrate 7 to produce a two-terminal LCD with a liquid crystal cell gap of 5 μm.

In the two-terminal element matrix array obtained as described above (see FIGS. 2(a) and (b)), the coupling capacitance between the data bus line and the pixel electrode is small, and the potential of the pixel electrode is lower than that of the data bus line. It is almost unaffected by the signal voltage on the line, making it possible to display more gradations.

8 [Example 3] Figure 5 (a) below. According to (b), T F T of the present invention
An example of -LCD will be described along with its manufacturing process.

On the same transparent insulating substrate 1 as in Example 1, photosensitive polyimide (manufactured by Toray Industries, Ltd., Photonice), which is the material of the low dielectric constant insulating film 12, was coated with a film thickness of 5 μm, which is the liquid crystal cell gap thickness. Same imitation as example 2, i? A TPT-LCD was fabricated by forming a resistive dielectric constant insulation layer 1d6 using i-photonic processing.

In the TFT-matrix array obtained as described above, the coupling capacitance between the source wiring and the pixel electrode is small, the potential of the pixel electrode is almost unaffected by the signal voltage on the source wiring, and it has more gray levels. It is now possible to display Also,
The spacer that maintains the cell gap of the liquid crystal display device can be made at the same time as the low dielectric constant insulating layer, which simplifies the process steps.

[Effects of the Invention] As described above, according to the present invention, it is possible to suppress the voltage fluctuation of the pixel electrode due to capacitive coupling, and crosstalk can be prevented. Therefore, more fine voltage control of the pixel voltage becomes possible, so that multi-gradation display becomes possible.

Furthermore, since a spacer for maintaining the cell gap of a liquid crystal display device can be created at the same time as forming a low dielectric constant insulating layer, the process steps can be simplified.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) show the TFT-L structure of the present invention.
It is an explanatory view of CD, (a) is a plan view, (b) is (a
) is a cross-sectional view of the portion indicated by AA' in the figure. Second
Figures (a) and (b) are explanatory diagrams of a two-terminal element according to the present invention, in which (a) is a plan view and (b) is indicated by AA' in the figure (a). FIG. Figure 3(a)
-(e) and FIGS. 4(a)-(d) are explanatory diagrams of the manufacturing process of the low dielectric constant insulating layer of the present invention, and FIGS. 5(a), (b)
) are explanatory diagrams of a TPT-LCD configured according to the present invention, in which (a) is a plan view, (b) is a cross-sectional view of the portion indicated by A-A' in the figure of (a), and the sixth Figures (a) and (b) are explanatory diagrams of a conventional TPT-LCD. Figure 7(a), (
b) is an explanatory diagram of a conventional two-terminal LCD. 1... Transparent insulating substrate 2... Thin film transistor 3... Pixel electrode 4... Source wiring 5... Gate wiring 6... Low dielectric constant insulating layer 7... Opposing transparent electrode substrate 8.・Liquid crystal layer 9 ・Data bus line 10 ・2-terminal element 11 ・Photoresist 12 ・Low dielectric constant insulating film 1 3 ・Mask patent application Toppan Printing Co., Ltd. Representative Suzuki Kazuoichi 217

Claims (3)

[Claims] (1) Thin film transistors and pixel electrodes are arranged in a matrix array on a transparent insulating substrate, source wiring is arranged in the column direction of the pixel electrode, and gate wiring is arranged in the row direction,
In the liquid crystal display device in which a liquid crystal layer is sandwiched between the transparent insulating substrate and the opposing transparent electrode substrate, a low dielectric constant insulating layer is formed on the source wiring and the gap between the pixel electrode and the source wiring. Matrix type liquid crystal display device. (2) Two-terminal elements and pixel electrodes are arranged in a matrix array on a transparent insulating substrate, data bus lines are arranged in the column direction of the pixel electrodes, and a liquid crystal layer is formed between the transparent insulating substrate and the opposing transparent electrode substrate. 1. An active matrix type liquid crystal display device comprising: a low dielectric constant insulating layer formed over the data bus line and the gap between the pixel electrode and the data bus line. (3) Claim (3) characterized in that the low dielectric constant insulating layer serves as a spacer that maintains a cell gap of a liquid crystal display device.
The active matrix liquid crystal display device according to 1) or (2).