JPH02277201A - Voltage-dependent nonlinear resistor and its manufacture - 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 nonlinear resistor and a method for manufacturing the same. More specifically, the voltage nonlinear resistor of the present invention has stable voltage-current characteristics and is useful for various uses such as abnormally high voltage absorption or voltage stabilization. In particular, it is suitable for use as a switching element in matrix-driven liquid crystal display devices and the like.

[Prior Art and Problems to be Solved by the Invention] Many proposals have been made in the past regarding voltage nonlinear resistors obtained by forming an insulating film on the surface of inorganic semiconductor fine particles.

For example, in Japanese Patent Application Laid-Open No. 62-190808, 8i20. A voltage nonlinear resistor obtained by forming an inorganic insulating film is disclosed. A resistor obtained from this resistor is characterized by a large voltage nonlinearity index α in a low current region and a small parallel capacitance. However, as shown in Figure 1 of the above publication, the inorganic semiconductor fine powder used in the above-mentioned resistor is non-spherical, and the lengths of its long axis and short axis are particularly large (different , many rectangular fine powders were mixed in, and the particle size distribution was wide.

Furthermore, in the manufacture of the above-mentioned resistor, Bi 2 tends to evaporate during the firing process, resulting in a problem that the characteristics of the resulting resistor vary widely.

The above-mentioned significantly non-spherical inorganic semiconductor fine powder is
There is no particular effect when the resulting highly non-spherical resistor is used as a thick film voltage non-linear resistor. However, when this resistor is used as a switching element in, for example, a liquid crystal display device using an active matrix drive method such as a liquid crystal television or a display for office automation equipment, the orientation of the aspherical resistor fine powder The contact area between the fine powder resistors changes, which often causes variations in the parallel capacitance of the resulting device, or the number of resistor fine powders present between the electrodes changes, thus causing variations in the parallel capacitance of the resulting device. Problems such as fluctuations in the varistor voltage occurred, and for this reason, the practical characteristics of the resistor were not sufficient.

Therefore, it has been desired to develop a voltage nonlinear resistor having even better voltage-current characteristics and a small parallel capacitance, and a method for manufacturing the same.

The present invention provides a voltage nonlinear resistor that has stable voltage-current characteristics, a small parallel capacitance, and is suitable for use in a thin film state, and a method for manufacturing the same. This is what I am trying to do.

[Means and actions to solve the problem]

The inventors of the present invention have conducted various studies on the development of voltage nonlinear resistors that have stable voltage-current characteristics, small parallel capacitance, and are stable. We have developed a voltage nonlinear resistor and its manufacturing method.

The voltage nonlinear resistor of the present invention is composed of inorganic semiconductor fine particles and an inorganic insulating film formed on the surface thereof,
The inorganic semiconductor fine particles have a substantially spherical shape, and the length of the major axis is ! , and the length of the short axis 12 II1/lz
is within the range of 1:1 to 1:3, and the inorganic insulating film essentially consists of oxides of Mn.COl and Al.

The method of the present invention for manufacturing the voltage nonlinear resistor includes at least two firing steps at a temperature of 1000° C. or higher, and at least one firing step performed at least between the firing steps. After the crushing process, has a spherical shape of X゛, the length of its major axis is l + the length of its minor axis! Prepare inorganic semiconductor fine particles having a ratio of 1:1 to 1:3 in the range of 1:1 to 1:3, and generate an inorganic oxide containing the inorganic semiconductor fine particles, Mn, Co, and Al. This mixture is fired at a temperature of 1000° C. or higher to form essentially Mn and C on the surface of the inorganic semiconductor fine particles.

and AI! It is characterized by forming an insulating film made of an inorganic oxide.

There are no particular limitations on the type of inorganic semiconductor used in the voltage nonlinear resistor of the present invention, but generally the main component is at least one selected from zinc oxide, barium titanate, silicon carbide, etc. It is preferable that Although there is no particular limitation on the size of such inorganic semiconductor fine particles, it is generally preferable that the average particle size is within the range of 1 to 20M, and even more preferably within the range of 3 to 10M. preferable.

In the resistor of the present invention, the inorganic semiconductor fine particles are
A beam has a spherical shape, and the length of its major axis! , and the length of the short axis! , is within the range of 1:1 to 1:3. This ratio β, /I! , is 1:1~
It is more preferable that the ratio is within the range of 1:1.5, especially 1:1.5.
: A shape closer to 1, that is, a shape closer to a perfect sphere is most preferable.

In the resistor of the present invention, an inorganic insulating film is formed on the surface of the semiconductor fine particles. This insulating film is formed of an insulating inorganic oxide.

The insulating coating of the resistor of the present invention essentially consists of Mn and C.

and an oxide of Al. There is no particular limitation on the blending ratio of these oxides, but MnO is 0.1-10 mol% and CO2O3 is 0.1-10 mol% relative to the amount of semiconductor fine particles.
Preferably, A 1203 is in the range of 1 to 10 mol %, and A 1203 is in the range of 10 −4 to 1 mol %. Such Mn・Co
- an inorganic oxide mixture consisting essentially of an oxide of Al,
A stable insulating film can be formed on the surface of the semiconductor fine particles without melting at the firing temperature.

There are no particular limitations on the weight and thickness of the insulating coating, but generally each is 10-10% of the amount of semiconductor particles.
4 to 10 mol%, preferably 1O-3 to 2.0 mol%
, and 0.001-5 M, preferably 0.01-5 M
It is preferably within the range of 14.

In the method of the present invention, the inorganic semiconductor producing raw material, for example,
A raw material consisting of at least one member selected from zinc oxide and zinc hydroxide is heated to a temperature of 1000°C or higher, preferably 1000°C to 1400°C, more preferably 1150°C.
It is subjected to at least two calcination steps at a temperature of ~1250<0>C, preferably for 1 to 5 hours, and at least one comminution step carried out at least between these calcination steps.

That is, before the first firing step, the semiconductor generation raw material is
And/or it may be subjected to an additional pulverization step after the final firing step. Moreover, the pulverization process may be performed two or more times between adjacent firing processes. Moreover, each pulverization step may be combined with a subsequent classification step.

Through the above-mentioned firing process and crushing process, the semiconductor-generating raw material changes into a semiconductor as described above, and at the same time, it has a nearly spherical shape, with the length of the major axis l and the length of the minor axis lx.
The ratio L #2 is 1 within the range of 1 to 1:3, and preferably fine particles having an average particle size of 1 to 20 are produced.

Next, the semiconductor fine particles and the insulating inorganic oxide-forming raw material compound are mixed. In this mixing step, the oxide-generating raw material compounds are converted into inorganic compounds constituting a predetermined insulating film, such as Mn and Co, through a firing step described later.
and oxides, carbonates, nitrates and hydroxides of AI, and the total amount thereof is preferably 10-4 to 10 mol% based on the amount of inorganic semiconductor fine particles in terms of oxide weight. , 10-' to 2.0-2 degrees is more preferable.

Next, this mixture is heated to a temperature of 1000°C or higher, preferably 1000 to 1400°C, more preferably 1100 to 12°C.
Calcinate at a temperature of 50°C. In this firing step, the inorganic oxide-generating raw material compound changes into a corresponding inorganic oxide, and this inorganic oxide is solid-dissolved on the surface of the semiconductor fine particles to form an insulating film.

The amount and thickness of this insulating coating are as described above.

The time for this firing step is not particularly limited, and is appropriately set depending on the raw material compounds used and the firing temperature, but is generally preferably within a range of 1 to 5 hours.

The resistor particles obtained by the firing process are subjected to a classification process, if necessary, to classify them into a predetermined particle size.

The resistor obtained by the above method is, for example, shown in FIG.
), it has a spherical particle shape and exhibits a stable varistor voltage.

Therefore, the voltage nonlinear resistor particles of the present invention are useful as constituent elements of switching elements for liquid crystal display devices.

〔Example〕

The invention will be further illustrated by the following examples.

Example 1 Zinc oxide powder with a particle size of 0.05 to 1 JIa was formed into pellets, then calcined at 1200°C for 2 hours, and then crushed and classified to obtain angular particles with a particle size of 5 to 10. . Next, this was subjected to secondary firing at 1200°C for 1 hour, and then
The particles were pulverized to obtain so-spherical fine particles having a particle diameter of 2 to 20-1, an average particle diameter of 5 to 10 μm, a long axis of 11.7, and a short axis to axis ratio of 1 to 1.5.

MnCO5 and CO2O relative to the amount of zinc oxide fine particles
.

0.5 mol% of each powder, Fuyobi^f (No, ),
・Add and mix 0.005 mol% of nH,O solution powder, bake this mixture at 1200°C for 1 hour, and then lightly crush and classify it to form a nearly spherical particle with a uniform particle size of 5 to IO-. A nonlinear resistor was obtained. The particles of this voltage nonlinear resistor had a spherical particle shape as seen in an electron micrograph as shown in FIG. 1(A).

50% by weight of glass powder and 5% by weight of binder (ethyl cellulose) with respect to the weight of the above voltage nonlinear resistance.
% by weight and a solvent were added to form a paste, and after printing on a substrate, heat treatment was performed at 450° C. to produce a voltage nonlinear element.

The voltage-current characteristics of this voltage nonlinear element are shown by curve A in FIG. The voltage nonlinearity index α of this device was 25 as shown in Table 1 when the device area was 1 ml and the distance between the electrodes was 30, which was large in the low current range. The varistor voltage (when a current of 10-6 amperes flows) is 2 with 50 measuring elements.
It was 8±3V and was well aligned.

Table 1 summarizes the conditions of Example 1.

Examples 2 to 7 In each of Examples 2 to 7, the same operations as in Example 1 were performed. However, in order to form an insulating film, MnO and Co were used at the composition ratio shown in Table 1. 03, and 120.
A mixture of these was used.

Table 1 shows the manufacturing conditions of this voltage nonlinear resistor and the electrical characteristics of the voltage nonlinear resistor element obtained therefrom.

Comparative Example 1 The operation described in Example 1 was repeated. However, B12D30 is used as a raw material compound for forming an insulating film without performing secondary firing.
．． 5 mol was used. That is, the particle size is 0.05 to IJ! After molding the zinc oxide powder of m into pellets, a second firing was performed at 1200° C. for 2 hours. The obtained particles have a particle size of 2 to 20μ
, has an average particle size of 5 to 10-1, and its major axis l+/minor axis 1
The 2 ratio was in the range of 1 to 5, and the shape was angular and non-spherical.

Then, B1□0. 0.5 mol % was added and mixed, and after baking at 1200°C for 1 hour, it was lightly crushed and classified to obtain a voltage nonlinear resistor with a particle size of 5 to 10p. The particle shape of this resistor in an electron micrograph is shown in Figure 1 (
B), which was a non-spherical body.

To this voltage nonlinear resistor, 50% by weight of glass powder, 5% by weight of binder, and 40% by weight of solvent were added to form a paste. After printing this paste on a substrate, it was heat-treated at 450°C. A voltage nonlinear element was fabricated by performing the following steps.

The voltage-current characteristics of this voltage non-linear element are shown in FIG. 2 by curves. As in Example 1, the element area was set to 1fflI.
112, the voltage non-linearity index α when the inter-electrode distance was 30 -, as shown in Table 1, was 6, which was small in the low current range. Its varistor voltage (
(when a current of 10-' ampere flows) was 27±7 V with 50 measuring elements, which was a relatively large fluctuation.

Comparative Example 2 The same operation as in Comparative Example 1 was performed. However, as shown in Table 1, instead of Bi2O, as in Example 1, Mn00.5 mol%, Co□Q, o, 5% Le
, A n 2030.005 mol % was used. The element area of the voltage nonlinear resistance element obtained in this way is 1 m
When the distance between m2 electrodes is 30-, the voltage non-linearity index α is 15 as shown in Table 1, and
It was small in the low current range.

The varistor voltage (when a current of 10 -6 amperes flows) was 27±5 V with 50 measuring elements, and had relatively large fluctuations.

Table 1 Example 8 10 g of voltage nonlinear resistor particles (varistor) prepared in Example 1, 5 g of glass powder, and 1 g of ethyl cellulose
and ethylcarpitol 5- were thoroughly mixed to prepare a paste. Predetermined pixel electrodes (5IIIIII
, printing the paste on a first glass substrate patterned with signal electrodes (pixel electrode-signal electrode distance: 50M) through a screen having a predetermined pattern;
This was heat-treated at 300 to 500° C. to produce a substrate in which each pixel electrode and signal electrode were bonded with a varistor film.

Separately, 20 g of 10% Pv^ aqueous solution and 150 g of dichroic dye
An emulsion prepared from 6 g of liquid crystal (trademark: E-44, manufactured by Merck & Co., Ltd.) containing 1.0 mg of dissolved liquid crystal was coated using a doctor blade on a second glass substrate on which predetermined scanning electrodes had been patterned with ITO in advance. Let this dry,
A polymer-dispersed liquid crystal layer (thickness: 15 mm) was formed. Both substrates were bonded together and the periphery of the formed composite was sealed to produce a liquid crystal display panel. An explanatory cross-sectional view thereof is shown in FIG.

As shown in FIG. 3, a plurality of pixel electrodes 11a
However, according to a predetermined pattern, the first transparent glass substrate 12
Further, a plurality of signal electrodes 13 are arranged adjacent to the pixel electrode 11a to supply electrical signals to the pixel electrode 11a. Further, a plurality of varistor films 14 (non-linear resistors) were arranged between the pixel electrode 11a and the signal electrode 13 adjacent thereto to connect them. Furthermore, the second transparent glass substrate 12b is arranged parallel to and spaced apart from the first glass substrate 12a, forming a gap therebetween, and the transparent scanning electrode 11b is
It was fixed to the lower surface of the second glass substrate 12b.

A polymer-dispersed liquid crystal layer 15 containing the liquid crystal was formed in the gap between the first glass substrate 12a and the second glass substrate 12b.

The arrangement relationship among the signal electrode 13, varistor film 14, and pixel electrode 11a is shown in FIGS. 4(A), 4(B), and 4.
This is shown in Figure (C).

As shown in FIG. 4(A), a plurality of pixel electrodes 11a are separately connected to the signal electrode 1 through the varistor film 14.
As shown in FIGS. 4(B) and 4(C), the pixel electrode 11a and the signal electrode 13 are fixed to the first glass substrate 12a. They were connected via a varistor film 14 made of varistor particles 14a.

When a driving circuit was connected between the signal electrode and the scanning electrode of the liquid crystal display panel device as described above, and this was driven at 100 V and a duty ratio of 1/64, a contrast ratio of 15 or more was obtained, and there was no crosstalk. A clear display was achieved.

〔Effect of the invention〕

The voltage nonlinear resistor obtained by the present invention is made by forming an insulating film made of Mn CO and Af oxides on approximately spherical inorganic semiconductor fine particles, and the voltage nonlinearity When a resistor element is fabricated, there is almost no variation in the contact area due to the orientation direction of the voltage nonlinear resistor fine particles that make up the resistor element, so there is no variation in parallel capacitance, and the contact between the fine particles is mainly point contact. Therefore, the parallel capacitance became small. Moreover, there is little variation in varistor voltage between elements, and the voltage-current characteristics are excellent.

[Brief explanation of drawings]

FIG. 1(A) is a schematic diagram showing the particle shape of the voltage nonlinear resistor of the present invention observed with an electron microscope, and FIG. 1(B) is a schematic diagram showing the particle shape of the voltage nonlinear resistor of the present invention observed with an electron microscope. FIG. 2 is a diagram showing voltage-current characteristics of voltage nonlinear elements fabricated from voltage nonlinear resistors of the present invention and conventional voltage nonlinear resistors; FIG. 4 is an explanatory cross-sectional view showing the structure of an example of a liquid crystal display panel device using the voltage nonlinear resistor of the present invention, and FIGS. 4(A), 4(B), and 4(C) are respectively FIG. 3 is an explanatory diagram showing an example of a connection between a pixel electrode and a signal electrode via a voltage nonlinear resistor; A: Voltage-current characteristic curve of the voltage nonlinear resistor element according to the present invention (Example 1) B: Voltage-current characteristic curve 11a of the resistor element according to the prior art (Comparative Example 1) ...pixel electrode, 11b...scanning electrode,
12a... First glass substrate, 12b... Second glass substrate, 13... Signal electrode, 14a... Varistor particle, 14... Varistor film, 15... Liquid crystal layer.

Claims (3)

[Claims] 1. It is composed of inorganic semiconductor fine particles and an inorganic insulating coating formed on the surface thereof, and the inorganic semiconductor fine particles have a substantially spherical shape, and have a length l_1 of the major axis and a length l_2 of the short axis. Ratio l_1/
l_2 is in the range of 1:1 to 1:3, and the inorganic insulating film essentially contains Mn, Co, and A.
A voltage nonlinear resistor, characterized in that it is made of an oxide of l. 2. An inorganic semiconductor-generating raw material is subjected to at least two firing steps at a temperature of 1000° C. or higher and at least one pulverization step performed at least between the firing steps, so that it has a substantially spherical shape and its Prepare inorganic semiconductor fine particles in which the ratio l_1/l_2 of the length l_1 of the long axis to the short axis l_2 is within the range of 1:1 to 1:3, and the inorganic semiconductor fine particles contain Mn, Co, and Al. , and a raw material compound that produces the inorganic oxide, and this mixture is fired at a temperature of 1000°C or higher to form an inorganic oxide of essentially Mn, Co, and Al on the surface of the inorganic semiconductor fine particles. A method for manufacturing a voltage nonlinear resistor, comprising: forming an insulating film consisting of: 3. A switching element for a liquid crystal display device, comprising the voltage nonlinear resistor according to claim 1 as a component.