JPS62190814A - Voltage nonlinear device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a voltage non-linear element whose resistance value changes depending on an applied voltage, and is useful for voltage stabilization, abnormal voltage control, and (a) IJ-Fuchs dynamic liquid crystal.

It is used in switching elements of display devices such as KL.

Conventional technology Conventional voltage nonlinear elements are made of zinc oxide (ZnO), bismuth oxide (Bi20.), and cobalt oxide (C'203).
+ Manganese oxide (MnO□), antimony oxide (Sb2
0. ) and other oxides to increase the
There are various types such as ZnO varistors sintered with carbon.

Among them, ZnO varistors are the most commonly used because of their high voltage nonlinearity index α and high surge resistance.

(Refer to Japanese Patent Publication No. 46-19472) Problems to be Solved by the Invention Conventional voltage nonlinear elements such as these, including ZnO varistors, have limitations in making the element thickness thin (several tens of μm or less). Therefore, the varistor voltage (current 1 to the varistor)
There is a limit to lowering the voltage (expressed as v11nm) when mA is applied, and it cannot be used as a protection element for low voltages or a voltage stabilizing element at low voltages. Further, as described above, since a high temperature process of 100° C. or higher is required, there is a problem that a voltage nonlinear element cannot be directly formed on a glass substrate or a circuit board. Furthermore, conventional devices have a large parallel capacitance, making them unsuitable for use as switching elements for liquid crystals, for example.

Means for Solving the Problem In order to solve this problem, the present invention involves solidifying a finely powdered semiconductor material with a thin insulation film removed with an insulating binder.
It is equipped with electrodes.

Effect: According to this configuration, a large voltage non-linearity index α can be obtained even in a low current range, and an element can be formed with a narrow distance between electrodes (several tens of μm or less), making it possible to reduce voltage. A suitable element can be obtained very easily. In addition, since it can be made without requiring high-temperature processes when solidifying it with a binder and forming elements, it is possible to form elements directly on circuit boards, allowing for a wide range of applications unimaginable with ZnO varistors and the like. This is something to look forward to.

Furthermore, since it is a solidified form of semiconductor material in the form of fine powder, there is point contact between the fine powders of each semiconductor material, and because the contact area is small, it is possible to obtain a small parallel capacitance, which is useful for devices such as liquid crystals. This means that an optimal element can be provided as a switching element.

Example Hereinafter, the present invention will be explained in detail based on examples.

First, fine particulate zinc oxide with a particle size of 0.06 to 1 μm is fired at 700 to 1300'G, and then the sintered ZnO is sintered with a particle size of 0.5 to 60 μm (average particle size of 1 to 1
0 μm), and 0.06 to 10 mo1% of cobalt oxide was added to the ZnO fine powder to form a powder of 1600 to 1350'.
C for 10 to 60 minutes to form an insulating film of cobalt oxide on the surface of the ZnO fine powder. Here, the surface of the fine powder ZnO contains CO□0. Approximately several dozen insulation coatings
It was observed that it was formed thinly, with a thickness of several hundred people.

Next, since the ZnO fine powder group with the Co2O3 insulating film formed on its surface adhered to each other with a weak force, it was loosened in a mortar or a bot mill to form a fine powder. Next, the Co2 obtained as above
Finely powdered ZnO with an O3 insulating film formed on its surface,
A polyimide resin was added as an insulating binder to bond the fine powders together and mixed. Here, as a binder, the solid content of polyimide resin is used as a solvent (for example, n-
It was diluted to Swt % based on methyl-2-pyrrolidone), and mixed with ZnO fine powder in an equal weight, for example, to form a paint. Next, the paint obtained as described above is applied to a glass substrate 3 provided with an ITO (indium tin oxide) electrode 1, as shown in FIG.
For example, apply it by screen printing.

On top of that is the same (glass substrate 4 provided with ITO electrode 2)
and placed at 280-400'C for 30 minutes.

After curing in the atmosphere, a voltage nonlinear element 5 is placed between the electrodes 1 and 2.
has been established. FIG. 1 is an enlarged sectional view of the voltage nonlinear element 5, in which 6 is ZnO fine powder and 7 is ZRI.

The Co2O3 insulating film 18 applied to the surface of the ZnO fine powder 6 is an insulating binder that mechanically connects the ZnO fine powders 6, and this binder 8 allows the Zn.

The fine powders 6 are solidified together. Figure 3 shows ITO
A case is shown in which a voltage nonlinear element 6 is constructed on a glass substrate 3 & on which electrodes 1a and 1b are provided.

Next, the voltage-current characteristics of the voltage nonlinear element created as described above will be explained. First, Figure 4 shows the second
The voltage-current characteristics of the configuration shown in the figure are compared with those of a conventional ZnO varistor.

The device of the present invention is made by first firing zinc oxide at 700'C, and adding Co20. After heat treatment at 900°C for 60 minutes, the average particle size was 5.
In a mixture of ~10 μm ZnO fine powder and binder in equal weight, the device area is 1-5 and the distance between electrodes is 30 μm.
The characteristics are shown when m is set. Now, as is well known, the voltage-current characteristics of a voltage nonlinear element are approximately expressed by the following equation.

I=KV" Here, E is the current flowing through the element, V is the voltage between the electrodes of the element, K is a constant corresponding to the resistance value of the specific resistance, and α is the exponent of the voltage nonlinear characteristic mentioned above. The larger the voltage nonlinearity index α, the better the voltage nonlinearity.

As shown in the characteristics in Figure 4, the conventional ZnO varistor shown by characteristic B has a voltage nonlinearity index α in the low current region.
is small, and cannot function as a good voltage nonlinear element at a current of 10 μm or less. On the other hand, it was shown that the device of the present invention, as shown by the characteristics, has a large voltage nonlinearity index α even in the low current range, and can sufficiently function as a voltage nonlinear device even in the current range of about 110 μm. There is. Furthermore, in order to express the varistor characteristics of a ZNO varistor, for example, the voltage that appears between the electrodes when a current of 1 mm is passed through the element is expressed as the varistor voltage v1.
This varistor voltage v, Ayu, and the voltage non-linearity index α are used. In the device of the present invention, as described above, the voltage non-linearity index α is large even in the low current range, and the varistor voltage can be expressed by, for example, v and 7 m as shown in FIG.

In this way, in the present invention, the varistor voltage can be made low because the element can be formed by narrowing the distance between the electrodes.

The reason why the voltage nonlinearity index α is large even in the low current range in the device of the present invention is not clear at present, but 1. This is thought to be due to the fact that since it is solidified, there is point contact between the respective semiconductor materials, so the contact area is small, and the bonding agent is insulating, so leakage current is small.

Here, the characteristics shown in Fig. 4 are as follows when the distance between the electrodes is 3
This is for an element with a thickness of 0 μm;
This is because the average particle size of the O fine powder is relatively large, 6 to 10 μm, and cannot be made any narrower. That is, the average particle diameter of the ZnO fine powder is 0.3
The present inventor has found that if a material with a diameter of ~3 μm is used, it is possible to create an element with a distance between one electrode of approximately 10 μm or less, and even in that case, good characteristics as shown in FIG. 4 can be obtained. This was confirmed through experiments.

FIG. 5 shows how the varistor voltage v, 11m, voltage nonlinearity index α, and parallel capacitance C change when the amount of cobalt oxide added is changed in the present invention. Here, other conditions such as the firing temperature of zinc oxide were the same as those in the case of FIG. 4.

As shown in FIG. 6, in the five devices of the present invention, the parallel capacitance of the conventional ZnO varistor is 1ooo to 20,000.
Although it is a PF, it is very small.

The reason why this parallel capacitance is small in the device of the present invention is as follows.
This is due to the small contact area between semiconductor materials as described above.

In addition, in the above embodiment, the semiconductor material is
Although ZnO has been described as an example, it goes without saying that other semiconductor materials may be used. Also,
Similarly, the material constituting the insulating film is Co2O3
but not limited to 1 Mu/, Ti.

Metal oxides such as Sr, Mg, Ni, Or, Si, etc. or organometallic compounds of these metals may be used, and these may be used alone or in combination.

In addition to polyimide resin, various other insulating binders for solidifying fine powder semiconductor materials are of course possible, including thermosetting resins such as phenol resin, furan resin, area resin, and melamine resin. , unsaturated polyester resin, diallyl phthalate resin, epoxy resin, polyurethane resin, silicone resin, etc. may also be used.

Effects of the Invention As is clear from the above explanation, the voltage nonlinear element of the present invention has a large voltage nonlinearity index α in the low current range, and an element with small parallel capacitance can be obtained, so that current consumption can be reduced. This makes it possible to provide an element that is optimal as a switching element for devices such as small liquid crystals and ICLs. In addition, since the device can be formed by narrowing the distance between the electrodes, a device with a low varistor voltage can be obtained, which, combined with the large voltage nonlinearity index α mentioned above, cannot be achieved with conventional ZnO varistors. It can be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages. Furthermore, since it can be easily manufactured without requiring a high-temperature process when forming an element by solidifying it with a binder, the element can be directly formed on a circuit board or a glass substrate. The voltage nonlinear element of the present invention having various features as described above is different from the conventional Zn
It can be expected to have a wide range of applications that cannot be imagined with O-varistors, and its industrial properties are outstanding.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of a voltage nonlinear element according to the present invention. FIGS. 2 and 3 are sectional views showing an embodiment in which the element of the present invention is provided on a glass substrate, respectively. FIG. 4 is a diagram showing the voltage-current characteristics of the device of the present invention and a conventional ZnO varistor, and FIG. 5 is a diagram showing the voltage-current characteristics of the device of the present invention and a conventional ZnO varistor
FIG. 3 is a diagram showing how the voltage non-linearity index α1 varistor voltage v, lt and parallel capacitance C change when the amount of addition is changed. 1.1&, 1b, 2, river...I'rO electrode, 3,32L
. 4...Glass substrate, 6...Voltage nonlinear element, 6...ZnO fine powder, 7...
Co20. Insulating coating, 8...Binding agent. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2rlA Figure 5 - Cθz0J addition (importation illusion)

Claims (1)

[Claims] A voltage nonlinear element characterized by comprising a finely powdered semiconductor material coated with a thin insulating film, hardened with an insulating binder, and equipped with an electrode.