JPH01224728A - Nonlinear two-terminal element - Google Patents

Abstract

PURPOSE:To facilitate extension of the area of a display panel and to simplify the producing method by forming a metal oxide thin film of a nonlinear two- terminal element consisting of three layers, namely, an electrode layer, the metal oxide thin film, and another electrode layer by the electrolytic deposition method. CONSTITUTION:A first electrode layer 11, a thin film layer 12 which is formed on the first electrode layer 11 by the electrolytic deposition method and contains a metal oxide, and a second electrode layer 14 formed on the second electrode layer 14 containing the metal oxide are provided. First and second electrode layers 11 and 14 consist of conductive films, and metallic thin films consisting of Cr, Ni, or the like formed by various methods such as the sputtering method and the spray method, transparent conductive films consisting of ITO (indium tin oxide), In2O3, or the like, or Ag paste, Cu paste, or the like where metallic particles are dispersed in a binder can be used as these conductive films. Thus, this method copes with mass production of elements in the active matrix system for large-area display, and the nonlinear two-terminal element is obtained which is produced by a small-sized equipment and has a low production cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nonlinear two-terminal element suitable for liquid crystal display panels and the like, particularly active matrix switching elements.

[Prior Art] As a method of increasing the number of pixels without reducing the contrast ratio of a display panel such as a liquid crystal display panel, an active matrix method in which each pixel is provided with a switching element such as a thin film transistor or a nonlinear two-terminal element is being considered. It has been.

In particular, an active matrix method using a nonlinear two-terminal element can be expected to have a higher yield because the manufacturing process of the element is simpler than an active matrix method using a thin film transistor.

FIG. 3(A) shows a cross-sectional view of a liquid crystal display panel using a nonlinear two-terminal element as a switching element, and FIG. 3(B) shows its equivalent circuit diagram. This display panel has a three-layer structure of a conductive film, an insulating film, and a conductive film, or a conductive film, a semiconductor film, and a conductive film. In the figure, 21 is a glass substrate, 22 is a transparent electrode,
23 is a polarizing film, 24 is a TN (twisted nematic) liquid crystal, 25 is an alignment film, 26 is an electrode layer, and 27 is an insulating layer or a semiconductor layer.

As a nonlinear two-terminal element used in a display panel, an M having a structure consisting of a conductive film - Ta, 05 (insulating film) - a conductive film is used.
A TM element is known (Japanese Unexamined Patent Publication No. 106181/1981).

In addition, hydrogenated amorphous silicon (a-5i:H) (
It consists of a three-layer structure in which a semiconductor film such as JP-A No. 60-138515) or hydrogenated amorphous silicon carbide (a-5iCx:H) (JP-A No. 60-50982) is formed between conductive films. Nonlinear two-terminal elements and devices in which these nonlinear two-terminal elements are connected in a ring have been studied.

[Problem to be solved by the invention] However, in order to obtain nonlinear characteristics in MIM devices, the thickness of the insulating film must be 500 to 600 Å or less, and it is difficult to uniformly form such an extremely thin film over a large area. It is difficult to do so.

On the other hand, in order to manufacture a nonlinear two-terminal device using semiconductor films such as a-5i: H, a-5iCx: H, etc.
Since it is necessary to use a sputtering method, a CVD method, etc., a vacuum device must be used. Therefore, large-scale equipment is required to mass-manufacture active matrix type display panels for large-area display, and manufacturing costs also increase.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, to be able to cope with the mass production of active matrix type elements for large-area displays, to be able to be manufactured with small equipment, and to have low manufacturing costs. The object of the present invention is to provide a nonlinear two-terminal element.

[Means for Solving the Problems] In order to achieve such an object, the present invention includes a first electrode layer and a metal oxide containing a metal oxide formed by electrolytic deposition on the first electrode layer. and a second electrode layer formed on the thin film containing the metal oxide.

As the substrate of the nonlinear two-terminal element of the present invention, for example, an insulating substrate made of glass, epoxy resin, polyester, polyurethane, polyimide, etc. can be used.

The first and second electrode layers of the nonlinear two-terminal element are made of conductive films, such as Cr, Ti, etc., formed by various methods such as sputtering, vapor phase, electroless plating, and spraying. , 8n, Ni, etc. metal thin films, TTO (
Indium tin oxide), transparent conductive films such as In2O5,
Ag paste with metal particles dispersed in binder, Au
Paste, Cu paste, etc. can be used. Note that the thickness of the first and second electrode layers is usually 0.1 to 5.
It is 0 μm.

As a method for forming a thin film layer containing a metal oxide (hereinafter simply referred to as a "metal oxide thin film"), an electrolytic deposition method can be used since a thin film layer with a large area can be easily formed.

Examples of metal oxides that can be formed by electrolytic deposition include lead oxide, copper oxide, iridium oxide, molybdenum oxide, and tungsten oxide. Among these, lead oxide is preferred. For example, for the formation of lead oxide by electrolytic deposition, usually 1 - 0.1 to 3 mol/Il of lead oxide, 2 basic inorganic compounds such as potassium hydroxide, hydroxide, sodium oxide, basic organic compounds, etc. , for example, 0.1 to 10 mol/l of basic compounds such as ammonia and triethylamine, and ■
An aqueous metal complex solution having a concentration of about 0.1 to 3 mol/It in which 0.1 to 5 mol/I of a ligand compound capable of forming a complex with lead is dissolved in a basic solution is used as the electrolytic solution.

Ligand compounds used in this electrolyte include aspartic acid, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, iminodiacetic acid, diaronic acid, nitrilotriacetic acid, and sodium salts of these ligand compounds. is used, and the ligand compound is not particularly limited as long as it can form a metal complex soluble in a basic aqueous solution.

To manufacture the nonlinear two-terminal device of the present invention by electrolytic deposition, first, the substrate on which the first electrode layer is formed by the method described above is immersed in the metal complex aqueous solution, and platinum, carbon, stainless steel, etc. is used as a cathode. A metal oxide is deposited on the first electrode layer by applying a voltage using the first electrode layer as an anode, thereby forming a metal oxide thin film.

In the electrolytic deposition method, the voltage applied between the cathode and the anode is usually 0.1 to 25 V (DC), preferably 0.5 to 1
5V (DC), and the current density of the current flowing through the electrode layer that deposits lead oxide is usually 0.01 to 50m A 7c
m2, preferably 0.1-20 mA/Cm2.

Further, the temperature of the electrolytic solution may be any temperature as long as the electrolytic solution does not solidify or boil, but it is preferably in the range of 20°C to 70°C.

By the electrolytic deposition method under the conditions described above, a resistivity of 1
A lead oxide thin film layer of 0-I to 104 Ω·cm is formed.

The thickness of this lead oxide thin film is usually 0.01 to 100 μm.
1 is preferably o, i to 10 μm; if the film thickness is too thin, defects will easily occur in the thin film, and if the film is too thick, the resistance of the nonlinear two-terminal element will become too large.

Note that in order to impart greater nonlinear characteristics to the obtained lead oxide thin film, it is preferable to perform cathodic reduction treatment.

This cathodic reduction treatment is an operation for adjusting the amount of oxygen in the obtained metal oxide thin film, and it is not preferable to completely reduce lead oxide.

Next, a method for cathodic reduction treatment of lead oxide thin films will be described.

Cathodic reduction treatment includes chromic acid, sulfuric acid, oxalic acid, tartaric acid, hydrochloric acid, nitric acid, phosphoric acid, oxalic acid, ammonium phosphate,
An aqueous solution in which ammonium oxalate, ammonium tartrate, ammonium hydroxide, sodium hydroxide, potassium hydroxide, etc. are dissolved, for example, from 0.1 to 10% by weight, preferably from 1 to 5% by weight, is used as the electrolytic solution.

A substrate with a lead oxide thin film formed thereon is immersed in this electrolytic solution, and a voltage is applied using platinum, stainless steel, a carbon compound, or the like as an anode and the lead oxide thin film as a cathode.

The voltage applied between the cathode and anode during cathodic reduction treatment is usually 0.
．． 1-1.5 V (in D), preferably 0.5-1
．． 3 V, and if the applied voltage is too low, a lot of time will be spent on the reduction process, and if the applied voltage is too high, good nonlinear characteristics will not be obtained.

The current flowing between the electrodes decreases over time from when voltage is applied.

Although the treatment time varies depending on the thickness of the lead oxide layer to be treated, it is preferable to carry out the treatment until the current density of the cathode becomes 0.05 mA/cm' or less in order to obtain good nonlinear characteristics.

The temperature of the electrolytic solution may be any temperature as long as the electrolytic solution does not solidify or boil, but is preferably in the range of 20 to 70°C.

Next, a second electrode layer is formed in the same manner as described above on the lead oxide thin film obtained as described above, thereby manufacturing a nonlinear two-terminal element.

In the present invention, the nonlinear characteristics of voltage and current are I-
This indicates that the V characteristic is represented by a curve as shown in FIG.

[Function] According to the present invention, since a metal oxide thin film having nonlinear characteristics can be formed by electrolytic deposition, a display panel that can be made larger and more uniform can be manufactured.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

Example 1 FIG. 1 shows an example of the present invention. The same figure (A) is a plan view,
Figure (B) is a sectional view taken along line AA' in Figure (A).

(1) A lithography process was performed on an ITO coated glass substrate 10 (manufactured by Makurazaki Vacuum Co., Ltd.) of 1 mm x 50 mm x 60 mm, followed by an etching process to form a transparent electrode 1.
3 was patterned.

Next, a nickel layer is formed on the substrate patterned with the transparent electrode 13 by nickel electroless plating, and then the scanning electrode 1 is formed by a lithography process and an etching process.
1 was formed into stripes.

(2) In a glass container, 98.2 g of lead oxide, 67.3 g of sodium hydroxide, and 235.8 g of disodium ethylenediaminetetraacetate were dissolved in pure water to prepare 1000 mft of electrolysis containing the metal complex.

(3) A scanning electrode as an anode and a platinum electrode as a cathode were immersed in the electrolyte obtained in (2) above, and a current of 3 mA/cm2 was passed on the anode side for 10 minutes at an electrolyte temperature of 60°C. However, a lead oxide thin film layer 12 having a thickness of about 2.5 μm was formed on the scanning electrode 11 .

(4) Furthermore, the lead oxide thin film layer 12 obtained in (3) as a cathode and the platinum electrode as an anode were immersed in a 3% by weight sulfuric acid aqueous solution, and a voltage of 1.1 μ was applied between the cathode and the anode at 25°C. was applied for 20 minutes.

(5) After cleaning the substrate, an electrode I4 made of Au paste was screen printed to obtain a substrate having a nonlinear two-terminal element shown in FIG. When the IV characteristics of the nonlinear two-terminal element formed on the substrate 10 were measured, nonlinear characteristics were confirmed.

Embodiment 2 FIG. 2 shows another embodiment of the wooden invention. 3A is a plan view, and FIG. 2B is a sectional view taken along the line AA' in FIG.

(1) l+n+++ x 50n+n+x [iQm
After plating the glass substrate 13 of 200 m to a thickness of about 2 μm using a nickel electroless plating method, the plating layer was patterned into stripes by a lithography process and an etching process to form scanning electrodes 11.

(2) A lead oxide thin film layer 12 was formed on the scanning type A in the same manner as in Example 1 (3).

(3) Furthermore, the ITO coating liquid 2 is screen printed on the lead oxide thin film layer 12', the transparent electrode 13 is formed as shown in FIG. 2, and the substrate having the nonlinear two-terminal element shown in FIG. Obtained. When the IV characteristics of the nonlinear two-terminal element formed on the substrate IO were measured, nonlinear characteristics were confirmed.

In the above embodiments, lead oxide was used as the metal oxide. However, the metal oxide in the present invention is not limited to lead oxide, and any metal oxide that can be formed by electrolytic deposition, such as copper oxide, iridium oxide, molybdenum oxide, or tungsten oxide, can be used in the display panel as in the above embodiment. A large area can be realized by a simple method.

[Effects of the Invention] As explained above, according to the present invention, a metal oxide thin film of a nonlinear two-terminal element having a three-layer structure of electrode layer/metal oxide thin film/electrode layer is formed by electrolytic deposition. Therefore, it is easy to increase the area of the display panel, and the manufacturing method is simple.

Further, unlike conventional nonlinear two-terminal elements, it is not necessary to use a vacuum device, so manufacturing equipment can be made smaller and manufacturing costs can be lowered.

Note that the nonlinear two-terminal device according to the present invention includes a liquid crystal display device, an electrochromic display device, a PLZT display device,
It is effective for driving fluorescent display elements, electroluminescence display elements, plasma emission display elements, etc.

[Brief explanation of the drawing]

FIGS. 1(A) and CB) are a plan view and a sectional view showing an embodiment of the present invention, respectively. FIGS. 2(A) and (B) are a plan view and a sectional view showing another embodiment of the wooden invention, respectively. 3(A) and 3(B) are a cross-sectional view and an equivalent circuit diagram showing an example of a conventional display panel, respectively, and FIG. 4 is a characteristic diagram showing a 1-V relationship of a nonlinear two-terminal element. DESCRIPTION OF SYMBOLS 10... Substrate, 11... Scanning electrode, 12... Lead oxide thin film layer, 13... Transparent electrode, 14... Paste electrode. Figure 3

Claims (1)

[Claims] 1) A first electrode layer, a thin film layer containing a metal oxide formed by electrolytic deposition on the first electrode layer, and a thin film layer containing a metal oxide formed on the thin film containing the metal oxide. A nonlinear two-terminal element comprising two electrode layers.