JPH03209435A - Active matrix type electrooptical device - Google Patents

Abstract

PURPOSE:To prevent the electrostatic destruction of an element by coating a substrate surface, where a switching element is formed, with an inorganic metal oxide film. CONSTITUTION:A device is composed of an upper substrate 1, column electrode 2, lower substrate 3, row electrode 4, liquid crystal layer 6 and inorganic metal oxide film 8. The whole surface of the lower substrate forming the switching element is coated with the inorganic metal oxide film 8. For this coating, solvent is applied to the surface of the substrate forming the switching element by printing. Further, by burning the film at a high temperature, organic substances in the printed film are almost removed and the inorganic metal oxide film 8 having satisfactory insulation ability is formed. Thus, the electrostatic destruction of the switching element can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix electro-optical device using a liquid crystal and a switching element, which is used in large image displays, computer terminals, optical shutters, and the like.

[Summary of the invention]

The present invention provides an active matrix electro-optical device in which a plurality of switching elements are formed on a substrate.
Coating the substrate surface with an inorganic metal oxide film containing SiO2, TiO2, and ZrO2 prevents electrostatic damage to the device during the manufacturing process, and reduces malfunctions caused by asymmetry of the switching device. It was to so.

[Conventional technology]

Liquid crystal display devices, which first appeared as displays in clocks, calculators, etc., have come to be used as electro-optical devices in a wide range of fields, including applications other than displays, such as computer terminals and optical shutters, as image quality has improved and they have become larger. Ta. In particular, active matrix electro-optical devices in which switching elements are built into each pixel on the surface of a substrate are expected to develop in the future due to their excellent display characteristics. The active matrix electro-optical device is MIM (Metal-1 nsulator).
-Metal) and MS I (Metal -3
Two-terminal type and three-terminal type TFT (Thin-Fi 1m-Tran) such as emi-Insulator)
sister).

A cross-sectional view of an MSI panel, which is a typical two-terminal active matrix electro-optical device, is shown in FIG. 2(a), a plan view of the pixel portion is shown in FIG. An enlarged cross-sectional view of is shown in FIG. 2(C). Figure 2 (a) (b)
) (c), 1 is an upper substrate, 2 is a column electrode, 3 is a lower substrate, 4 is a row electrode, 5 is a pixel electrode, 6 is a liquid crystal layer, and 7 is a nonlinear film.

It has a structure in which an electrically nonlinear film 7 such as SiNx is sandwiched between a row electrode 4 and a pixel electrode 5, and the entire structure constitutes a switching element. m row electrodes 4, column electrodes 7
If there are n pieces, it becomes an active matrix type electro-optical device with mXn pixels.

Next, the operation will be explained. The nonlinear film 7 has a property that its resistance is high at low voltages, but its resistance decreases as the voltage increases. Therefore, when an ON voltage is applied to the liquid crystal layer 6, the nonlinear film 7 becomes conductive and can write charges to the pixel electrode 5, but when an OFF voltage is applied, the nonlinear film 7 almost becomes an insulator and stores charges. retains the charged charge. By controlling the voltage applied to the liquid crystal layer 6 with a switching element in this way, the same good contrast and viewing angle characteristics as in static drive can be obtained in matrix drive.

[Invention or problem to be solved]

However, conventional active matrix electro-optical devices have two major drawbacks. One is that the switching element is easily destroyed by static electricity generated during the manufacturing process, and the other is that malfunction may occur due to the asymmetry of the switching element.

Malfunctions due to element asymmetry will be briefly explained. FIG. 3 is a diagram showing the current-voltage characteristics of the switching element, where the horizontal axis is the voltage and the vertical axis is the logarithm of the current. SiNx
In a switching element using a nonlinear film such as, even if the applied voltage is the same, the magnitude of the current will differ if the polarity changes.

For example, it can be understood from FIG. 3 that even if the voltage is the same, 2V, the current value differs by ΔI depending on the polarity.

For this reason, in the conventional active matrix electro-optical device shown in Figure 2, even if an AC voltage is applied from the drive circuit, a DC bias is applied to the voltage applied to the liquid crystal layer through the element, which causes a decrease in response speed. This often resulted in malfunctions such as extremely slow speeds or abnormal displays.

[Means to solve the problem]

The present invention was made to solve the above-mentioned drawbacks, and the substrate surface on which switching elements are formed is made of SiO2,
Coating with an inorganic metal oxide film containing TlO2 and ZrO2 as components prevents electrostatic damage to the device and reduces malfunctions caused by asymmetry of the device.

[Effect]

By coating the substrate surface with an inorganic metal oxide film, a good insulating film is formed between the liquid crystal layer and the switching elements, so the direct current component of the applied voltage is almost completely cut off and only the alternating current component is applied to the liquid crystal layer. Added. Therefore, malfunctions caused by element asymmetry can be almost completely prevented. Furthermore, if the surface of the switching element is coated, there is almost no risk of destroying the element due to static electricity generated during the manufacturing process.

Hereinafter, the present invention will be explained in detail with reference to Examples.

〔Example〕

FIG. 1 is a sectional view of an active matrix electro-optical device of the present invention. In FIG. 1, 1 is an upper substrate, 2 is a column electrode, 3 is a lower substrate, 4 is a row electrode, 6 is a liquid crystal layer, and 8 is an inorganic metal oxide film. The electro-optical device shown in FIG. 1 is exactly the same as that shown in FIG. 2(b) except that an inorganic metal oxide film 8 is coated on the entire surface of the lower substrate on which switching elements are formed, so a plan view is omitted.

Next, a method for forming the inorganic metal oxide film 8 will be explained step by step.

(1) Organic compounds of S102, TiO2, and ZrO2 are mixed in an appropriate ratio and dissolved in a solvent such as hexylene glycol.

(2) The above solution is applied by printing onto the substrate surface on which the switching elements are formed.

(3) Dry the printed film at about 100°C.

(4) Irradiate the film with UV light using a high-pressure mercury lamp.

(5) Baking the film at about 300°C. By firing at a high temperature, most of the organic matter in the printed film is removed, and an inorganic metal oxide film 8 with good insulation properties is formed.

In the above formation method, SiO2, TiO2, ZrO
By changing the ratio of 2, the refractive index of the inorganic metal oxide film 8 can be changed, so the reflectance or transmittance of the entire electro-optical device can be optimized by taking into consideration the refractive index of the lower substrate 3, pixel electrodes, etc. The proportions of the three ingredients are determined so that In some cases, the optimum refractive index may be obtained with two of the three components. Furthermore, in this example, printing was used as a method of applying the solution onto the substrate, but it is understood that using a method such as removing unnecessary portions after applying the solution with a spinner will not affect the present invention at all. Needless to say. The lower substrate 3 on which the inorganic metal oxide film 8 has been formed in the manner described above is then bonded to the upper substrate 1 and liquid crystal is further encapsulated to complete the electro-optical device shown in FIG.

When the active matrix electro-optical device shown in FIG. 1 was operated, no malfunctions that could be attributed to the asymmetry of the switching elements were observed, and extremely good operating characteristics were exhibited. Furthermore, electrostatic damage to switching elements, which had often occurred during the manufacturing process up to that point, was completely eliminated, and yields were dramatically improved.

〔Effect of the invention〕

As detailed above, according to the present invention, by adding an inorganic metal oxide film, it is possible not only to reduce malfunctions of active matrix electro-optical devices, but also to prevent electrostatic damage to switching elements during the process. I can do it.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an active matrix electro-optical device of the present invention, and FIG. 2 is a diagram of an MSI panel that is a typical active matrix electro-optical device.
3 is a cross-sectional view, (b) is a plan view of the pixel portion, (c) is an enlarged cross-sectional view of section A-A'' in (b), and FIG. 3 is a diagram showing the current-voltage characteristics of the switching element. 1. ... Upper substrate 2 ... Column electrode 3 ... Lower substrate 4 ... Row electrode 5 ... Pixel electrode 6 ... Liquid crystal layer 7 ... SiNx layer - - Inorganic metal oxide film or more

Claims (3)

[Claims] (1) In an active matrix electro-optical device in which a liquid crystal is sealed between two substrates and a plurality of switching elements are formed on the inner surface of at least one of the substrates, the surface of the substrate on which the switching elements are formed is made of an inorganic metal. An active matrix electro-optical device characterized by being coated with an oxide film. (2) The inorganic metal oxide film is SiO_2, TiO_2
The active matrix electro-optic film according to claim 1, which is a film formed by applying an organic compound containing ZrO_2 as a product dissolved in a solvent to the substrate surface, irradiating it with UV light, and further heating it. Device. (3) The switching element is SiNx, SiOx, S
2. The active matrix electro-optical device according to claim 1, which is a nonlinear resistance element constructed using a film having electrically nonlinear characteristics such as iCx.