JPH0555010A - Manufacture of voltage-dependent nonlinear element - Google Patents

Abstract

PURPOSE:To manufacture a voltage-dependent nonlinear element whose manufacture is easy and whose irregularity in a varistor voltage is small. CONSTITUTION:ZnO particles having a particle size of 0.05 to 1mum are heated and baked; their sintered substance is crushed to form sintered-substance particles 11; an insulating bonding material is added to and mixed with the sintered-substance particles 11 so as to be paintlike. This mixture is arranged between electrodes 2, 2 and heated. Thereby, a voltage-dependent nonlinear element 1 is manufactured. A low-melting-point glass 12 (e.g. lead glass) which contains one or more kinds out of Co, Mn, Phi, Pr, Sb and Ti is used as the bonding material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear element whose resistance value changes according to an applied voltage.
It is used as a switching element of a display device such as L.

[0002]

2. Description of the Related Art A conventional voltage non-linear element is zinc oxide (Z
nO), bismuth oxide (Bi₂O ₃), Cobalt oxide
(CoO), manganese oxide (MnO₂), Antimony oxide
(Sb₂O₃) And other oxides,
There are various types such as varistor sintered at 1350 ° C.
It Among them, the ZnO varistor is a voltage nonlinear index α,
Most commonly used due to its high ruggedness
(See Japanese Patent Publication No. 46-19472).

Such a conventional voltage non-linear element is Z
Starting with nO varistor, the device is thin (several tens μ)
However, there is a limit to lowering the varistor voltage (represented by the voltage V1mA when a current of 1 mA is applied to the varistor), and there is a limit to lowering the varistor voltage. It could not be used as a voltage stabilizing element. Further, as described above, there is a problem that the voltage non-linear element cannot be directly formed on the glass substrate or the circuit substrate because a high temperature process of 1000 ° C. or higher is required at the time of sintering. Furthermore, the conventional one has a problem that it has a large parallel capacitance and is unsuitable as a switching element for liquid crystal, for example.

In order to solve this problem and use it as a switching element of liquid crystal, for example, a group of particles mainly composed of semiconductor-made ZnO sintered particles and having a thin insulating film formed on the surface thereof A voltage non-linear element composed of a body has been developed (for example, Japanese Patent Laid-Open No. 62-190).
801). This method is characterized in that a low voltage and excellent voltage non-linearity can be obtained relatively easily, and a parallel capacitance can be reduced.

This method will be described in more detail. First, Z
nO powder, or the one with a small amount of additives added to it
Bake at a high temperature of 00 ° C. or higher. The sinter thus obtained is crushed to an average particle size of 1 to 20 μm to obtain sinter particles. Oxides such as Bi, Co, Mn, Pr, and Sb as high resistance layer compounds are added to the sintered particles, and the particles are fired at a temperature of 700 ° C. or higher. As a result, the individual surfaces of the sintered particles are covered with the high resistance layer containing these additive components. The voltage non-linear element is one in which the sintered particles having the high resistance layer formed on the surface are fixed with an inorganic or organic binder and an electrode is attached.

The voltage-nonlinear element thus obtained exhibits a very steep nonlinearity in its voltage-current characteristic. When the microstructure is compared with a ZnO varistor, in the ZnO varistor, fine crystal particles are in surface contact with each other through the high resistance layer, whereas in this voltage nonlinear element, the fine crystal particles are in the high resistance layer. Through point contact. Therefore, the parallel capacitance of the voltage nonlinear element is orders of magnitude smaller than that of the conventional ZnO varistor. This means that when this element is used as an active element in liquid crystal matrix driving, there is no loss due to electrostatic capacitance, which is suitable for high duty driving.

Further, in this conventional method, it is also possible to form varistor by mixing varistor particles (sintered body particles) prepared in advance with a binder to form a paste, which is printed on a substrate, baked and cured. It is possible. Various attempts have been made to use a varistor as an element for driving an active matrix of a liquid crystal. However, the problems that hinder practical application are that it is difficult to make a device with a low varistor voltage, and there are variations in characteristics.

Since the varistor voltage is proportional to the distance between the electrodes, the distance between the electrodes may be shortened in order to obtain a low varistor voltage. Even if the electrode spacing is the same, the varistor voltage can be changed by controlling the number of varistor particles arranged in series between the electrodes. That is, when the particle size of the varistor particles is changed, the varistor voltage changes accordingly. For example, if the particle size is doubled, the varistor voltage will be halved. The varistor element obtained by the above method by controlling the distance between the electrodes and the particle size is useful as an active matrix driving element for liquid crystal. Further, even if the distance between the electrodes is in the range of 10 to several hundreds of μm, it is possible to freely obtain the one having excellent characteristics at a varistor voltage of 10 V or more.

[0009]

However, the voltage non-linear element obtained by the latter conventional method (the latter publication) is
There are the following problems. That is, when the voltage non-linear element is used as a liquid crystal matrix driving element, one varistor should be formed on each ITO pixel on the ITO substrate. For example, if the number of pixels is 640 × 480, it is necessary to form that many varistor arrays on the substrate. Therefore, it is required to produce such a large number of varistors with a high yield and suppressing variations.

Therefore, in the above-mentioned conventional manufacturing method using the sintered body particles, a high resistance layer of Mn, Co or the like can be uniformly formed on the surface of the sintered body particles made into semiconductor with respect to each ZnO sintered body particle. Is essential. For this purpose, the sintered particles were sprinkled with an oxide such as Mn and Co and then fired again to pulverize the particles again. However, with this method, not all of the sintered particles having a high-resistance layer formed are crushed along the high-resistance layer during crushing, and even if the crushing method is carefully selected, all of the sintered particles will eventually be burned. There is no guarantee that the surface of the bound particles is covered with the high resistance layer. This manifests itself as a deterioration in the final varistor characteristics and variations.

As described above, according to the conventional manufacturing method, Mn, Co
The above-mentioned high resistance layer compound is sprinkled on the sintered body particles, and a complicated manufacturing process of re-baking and re-grinding is required, and the obtained voltage non-linear element has a large variation in varistor voltage. The inventors of the present invention have made extensive studies to solve the above problems, and have completed the present invention. An object of the present invention is to provide a method of manufacturing a voltage non-linear element which is easy to manufacture and has little variation in varistor voltage.

[0012]

According to the present invention, ZnO powder is heated and fired, and the sintered body is crushed to form sintered body particles, and an insulating binder is added to and mixed with the sintered body particles. In the method for manufacturing a voltage non-linear element by arranging a plurality of electrodes between a plurality of electrodes and then performing heat treatment, the binder is C
A method of manufacturing a voltage non-linear element, characterized in that it is a powder of a low melting point glass containing at least one additive element selected from the group consisting of o, Mn, Bi, Pr, Sb and Ti. What is most noticeable in the present invention is that the binder is one of Co (cobalt), Mn (manganese), Bi (bismuth), Pr (praseodymium), Sb (antimony), or Ti (titanium). This is to use a powder of low melting point glass containing the above-mentioned additional elements.

The above-mentioned additional elements are added in the form of oxides in the low melting point glass. In addition, the additive element is 0.1 to 0.1% in the low melting point glass when converted to each corresponding oxide.
It is preferably contained at 30 mol%. Here, the corresponding oxide is CoO for Co, Mn for MnO ₂ , Bi for Bi ₂ O ₃ , Pr for Pr ₆ O ₁₁ , Sb for Sb ₂ O ₃ ,
Ti means TiO ₂ . If it is less than 0.1 mol%, no improvement in the characteristics of the voltage non-linear element is observed, while if it exceeds 30 mol%, there is a possibility that the ZnO particles are difficult to bond at low temperature.

Further, as a low melting point glass which becomes a base when the above-mentioned additional elements are added, PbO-SiO ₂ -B ₂
Examples include O ₃ -based lead glass and ZnO—B ₂ O ₃ —SiO ₂ -based zinc glass. In the present invention, a binder obtained by incorporating the above-mentioned additional element into these low melting glass is used. Moreover, as a low melting point glass, PbO is 40
Lead glass consisting of ˜95 mol%, SiO ₂ of 0 to 10 mol%, B ₂ O ₃ of 1 to 50 mol%, and the additive element of 0.1 to 30 mol% in terms of the corresponding oxide is used. You can also In this case, the bondability of ZnO particles is excellent especially at low temperatures.

In the present invention, the sintered particles are obtained as follows. That is, first, as in the conventional case, ZnO
The powder (zinc oxide powder) aggregate is heated to 1000 to 1350 ° C.
In step 2, the particles are heated and fired to make the particles larger and to be made into a semiconductor. The above ZnO powder has, for example, a particle size of 1
A fine powder having a size of μm or less is used. Next, the sintered body obtained by the above heating and firing is pulverized. As a result, ZnO sintered particles are obtained. In addition, the above-mentioned sintered particles are ZnO.
Not only the Bi, Co, Mn, P on the surface of the particles
It is also possible to use one having a high resistance layer made of one or more kinds of compounds for a high resistance layer containing either r or Sb. The formation of such a high resistance layer is performed by once producing the sintered body particles as described above, adding the compound for a high resistance layer to the sintered body particles, re-firing, and loosening the re-sintered body. .. Then, the binder according to the present invention is added to the sintered particles having the high resistance layer thus formed to bond them.

As the above-mentioned compound for the high resistance layer, Bi ₂ O
₃ , CoO, MnO ₂ , Pr ₆ O ₁₁ , Sb ₂ O ₃ and the like. In addition to these, as additional components, Al (aluminum), Ti (titanium), Sr (strontium), Mg (magnesium), Ni (nickel), Cr
Metal oxides of elements such as (chromium) and Si (silicon), or organic compounds of these metals can also be used.

Further, the above-mentioned insulating binder according to the present invention is added to and mixed with the above-mentioned sintered body particles to form a paint material, and the paint material is applied between a plurality of electrodes provided on an insulating substrate. After that, heat treatment is performed to obtain a voltage non-linear element.
This heat treatment is usually performed at 300 to 550 ° C. Further, the binder facilitates forming a paste by mixing an organic binder such as ethyl cellulose with the low melting point glass powder when mixing with the sintered particles. The organic binder is burned off during the heat treatment. The above-mentioned binder is Z
It is preferable to add 10 to 100% by weight to the nO powder. If it is less than 10%, the coupling is insufficient, and if it exceeds 100%, the function of the voltage non-linear element may deteriorate.

[0018]

FUNCTION AND EFFECT In the present invention, the above-mentioned sintered particles are bonded by the low melting point glass containing the above-mentioned additional elements such as Co, Mn and Pr. And these are arrange | positioned between electrodes and it heat-processes and a voltage nonlinear element is manufactured. Therefore, during this heat treatment, additional elements such as Co, Mn, and Pr act on the surface of the sintered body particles to generate varistor characteristics.

Further, the voltage non-linear element obtained by the present invention has a large voltage non-linear index α in the low current region and a small variation in characteristics. Therefore, it is an optimal element as a switching element for devices such as liquid crystal and EL that consume little current. In addition, a low varistor voltage is obtained, and in combination with the large voltage non-linearity index α, a protection element for a low voltage IC and a voltage stabilization element at a low voltage, which cannot be dealt with by a conventional ZnO varistor. Can be used as

Further, in the present invention, as in the conventional case,
The complicated process of sprinkling ZnO powder with Mn, Co, etc., and then re-sintering and re-grinding becomes unnecessary, and the manufacturing is easy.
Further, since the device is formed by solidifying with a binder using low melting point glass, a high temperature process is not required in the device manufacturing process. Therefore, the element can be directly formed on the circuit board or the glass substrate. As described above, according to the present invention, it is possible to provide a method of manufacturing a voltage non-linear element which is easy to manufacture and has little variation in varistor voltage.

[0021]

【Example】

Example 1 A method of manufacturing a voltage non-linear element according to an example of the present invention will be described. First, the voltage non-linear element to be obtained according to the present invention will be described with reference to FIGS. First, the voltage non-linear element 1 shown in FIG. 1 has ITO (Indium-Indium) between glass substrates 3 and 3 as insulators.
The element body 10 is formed through the (tin oxide) electrodes 2 and 2. The element body 10 is composed of sintered particles 1 of ZnO.
1 and a low melting point glass 12 containing additional elements such as Mn and Pr. FIG. 2 is a side view showing the entire periphery of the element body in the voltage nonlinear element 1 shown in FIG. In addition, FIG. 3 shows a voltage nonlinear element 4 having another structure. The voltage non-linear element 4 is
The electrodes 21 and 21 are provided on one glass substrate 3, and the element body 10 similar to the above is formed between the electrodes 21 and 21.

Next, in manufacturing the voltage nonlinear device 1 shown in FIG. 1, first, ZnO powder is heated and fired, and the obtained sintered body is crushed to obtain ZnO sintered body particles 11
And Then, a binder made of powdered low melting point glass 12 and an organic binder is added to and mixed with the sintered particles 11 to form a paint. Next, as shown in FIG. 1, the paint is applied by screen printing or the like on the ITO electrode 2 formed on the glass substrate 3. Then, the ITO electrode 2 which is also separately formed on the glass substrate 3 is placed on the paint layer.

Thereafter, these are, for example, 300 to 500
The organic binder in the binder is burned off by heat treatment in the atmosphere at ℃ for 10 to 30 minutes. Further, by this, the low melting point glass 12 in the binder is melted, the sintered body particles 11 are solidified, and these are bonded to the ITO electrode 2. In addition, the above-mentioned sintered body particles 11 are separately provided with M for forming a high resistance layer.
When nO ₂ powder was added and re-fired and the sintered body was loosened into particles, the surface of the sintered body particle 11 was coated with a high resistance layer coating of MnO ₂ with a thickness of several tens to several hundreds of angstroms. Has been done. Then, in this case, the sintered body particles having the high resistance layer coating are mixed with the binder in the same manner as described above to form a paint.

Example 2 Low melting glass having various compositions shown in Table 1 was prepared,
As a result, a voltage non-linear element having bonded sintered body particles was produced. Then, for each voltage non-linear element, the non-linearity index α, insulation, and durability were measured. The results are shown in Table 2. That is, ZnO powder having a particle size of 0.05 to 1 μm was heated and baked at about 1000 ° C. to obtain a sintered body. Then, the sintered body is pulverized by a pulverizer to obtain an average particle size of 1
It was made to be a sintered body particle of ˜20 μm. Next, 55 wt% of the sintered particles were added and mixed with 45 wt% of the binder containing the lead glass-based low melting point glass shown in Table 1 above to form a paint. The binder is composed of 30 wt% of the low melting point glass powder and 8 wt% of ethyl cellulose as an organic binder. Then, as shown in Example 1, the above-mentioned paint was applied by screen printing onto the electrode bonded to the glass substrate, the electrode similarly provided on the glass substrate was overlaid, and heat-treated in the atmosphere at 440 ° C. for 60 minutes. , A voltage non-linear element was obtained.

For this voltage non-linear element, as shown in Table 2, variations in varistor voltage, non-linearity index α, which will be described later, insulation and durability were measured. In the table, the variation of the varistor voltage is 10%.
When it is less than 0, it is indicated by ◯, and when it is 10 to 20%, it is indicated by Δ.
Insulation is the magnitude of the amount of current that flows when a voltage of 10 V is applied. In the table, ○ indicates that the amount of current is 10 ^-11 A.
Is less than, △ is near 10 ^-11 A, ×
Indicates the case where it is larger than 10 ⁻¹¹ A. The durability was measured by the voltage-current characteristic measurement method. Here, the durability is obtained from the measurement results of the first time and the tenth time. In the table, ◯ indicates that the characteristics did not deteriorate, and Δ indicates that the characteristics deteriorate.

As is known from Table 2, Sample No. 1 according to the present invention. 1 to 7 have low varistor voltage variations.
Further, these are all comparative sample Nos. Which do not use the low melting point glass binder of the present invention. It has a high nonlinearity index α as compared to C1. Among them, the sample No. 2, 4, 7
Indicates an excellent nonlinearity index α. Comparative sample No. C2 uses a resin as a binder, and its non-linearity index α is low. Further, in terms of insulation and durability, the element of the present invention is the same as or superior to the comparative samples C1 and C2.

[0027]

[Table 1]

[0028]

[Table 2]

Example 3 MnO ₂ and CoO as compounds for the high resistance layer were added to and mixed with the sintered body particles shown in Example 2 and re-baked to prepare a voltage non-linear element. That is, to 100 mol% of the sintered particles obtained in the same manner as in Example 2, 0.5 mol% each of MnO ₂ and CoO as a compound for the high resistance layer were added, and these were re-fired at 1200 ° C. for 60 minutes. did. Then, the obtained sintered body is loosened, and MnO ₂ and C
Resintered body particles having a high resistance layer of oO were obtained. Further, as in the case of Example 1, the re-sintered body particles are shown in Table 1.
A voltage non-linear element was prepared by adding the binder containing the low melting point glass shown in (3). The results are shown in Table 3 as in Example 2.
It was shown to.

As is known from Table 3, the sample No. The elements 11 to 17 have low varistor voltage variations and exhibit a higher nonlinearity index α than the comparative samples C11 and C12. In addition, with respect to insulation and durability, results similar to or better than those of the comparative example can be obtained.

[0031]

[Table 3]

Example 4 Next, the voltage-current characteristics of the voltage non-linear element will be described with reference to FIG. In the figure, the characteristics A and B are
The voltage non-linear element of the present invention (Sample No. 2 and No. 1)
The characteristic D of 2) is the conventional ZnO varistor (Comparative Example No.
The characteristic C of C3) is the conventional voltage non-linear element (Comparative Example N).
o. The characteristic of C1) is shown. This voltage non-linear element has an element area of 1 mm ² and a distance between electrodes of 30 μm.

The above comparative example No. C3 (conventional ZnO varistor) was created under the following conditions. That is, Zn
O powder 98.5 mol% and Bi ₂ O ₃ , CoO, MnO ₂
0.5 mol% of each powder was mixed, molded, and fired at 1250 ° C.

As is well known, the voltage-current characteristic of the voltage non-linear element is approximately [I-KV
α]. Here, I 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 index of the above-mentioned voltage non-linearity characteristic. The larger the voltage non-linearity index α, the better the voltage non-linearity. In addition, in order to express the varistor characteristics in a ZnO varistor, for example, the voltage appearing between the electrodes when a current of 1 mA is applied to the element is called the varistor voltage V (lmA). The non-linear index α and are used.

As shown in the characteristics of FIG. 4, the conventional ZnO varistor shown in the characteristics D (Comparative Example N
o. C3) has a small voltage non-linearity index α in the low voltage region, and cannot function as a good voltage non-linearity device at a current of 10 ⁻⁴ A or less. On the other hand, the above-mentioned conventional voltage non-linear element (Comparative Example No. C1) has a large voltage non-linear index α even in the low current region as shown by the characteristic C, and is sufficient even in the current region of about 10 ^-10 A. It is shown that it can exhibit the function as a voltage non-linear element. Next, the voltage of the voltage non-linear element in the present invention-
The current characteristics are the characteristics A (Sample No. 2) and B (Sample N).
o. As shown in 12), the low melting glass does not contain the additive element relating to the present invention, and the comparative example No. It can be seen that the characteristics in the low current region are further improved as compared with C1. Therefore, it can be seen that the varistor voltage V (1 mA) can be further lowered.

The characteristics shown in FIG. 4 are for an element having an interelectrode distance of 30 μm as described above.
This is because the average particle diameter of ZnO powder is relatively large, that is, 5 to 10 μm, so that it cannot be further narrowed. The varistor voltage can be lowered by reducing the distance between the electrodes. That is, if ZnO powder having an average particle size of 0.3 to 3 μm is used, an element having an interelectrode distance of about 10 μm or less can be produced, and good characteristics similar to those shown in FIG. 4 can be obtained. Be done.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a voltage non-linear element according to a first exemplary embodiment.

FIG. 2 is a side view of the voltage non-linear element according to the first embodiment.

FIG. 3 is a side view showing another voltage non-linear element according to the first embodiment.

FIG. 4 is a voltage-current characteristic diagram of the voltage non-linear element of the present invention and Comparative examples C1 and C3 in Example 4.

[Explanation of symbols]

 1. ． ． Voltage non-linear element, 11. ． ． Sintered body particles, 2. ． ． ITO electrode,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isamu Masuyama 2-3-3 Hiyoshidai, Takatsuki City, Osaka Prefecture Masuyama Research Institute of Technology

Claims (4)

[Claims] 1. A ZnO powder is heated and fired, and a sintered body thereof is crushed to form a sintered body particle, and an insulating binder is added and mixed to the sintered body particle, which is then mixed into a plurality of electrodes. Placed in between
In the method of manufacturing a voltage non-linear element by heat-treating thereafter, the binder is Co, Mn, Bi, Pr, Sb and T.
A method of manufacturing a voltage non-linear element, which is a powder of a low melting point glass containing any one or more additional elements of i. 2. The low-melting glass according to claim 1, wherein the additive element is 0.1 to 30 in terms of each corresponding oxide.
A method of manufacturing a voltage non-linear element, characterized in that the element is contained in mol%. 3. The low melting point glass according to claim 1, wherein PbO is 40 to 95 mol%, SiO ₂ is 0 to 10 mol%, B ₂ O ₃ is 1 to 50 mol%, and each of the additive elements is A method for producing a voltage non-linear element, which is a lead low-melting point glass containing 0.1 to 30 mol% of the corresponding oxide. 4. The sintered body particle according to claim 1,
A method of manufacturing a voltage non-linear element, characterized in that it has on its surface a high resistance layer made of one or more kinds of compounds for high resistance layers containing any of Bi, Co, Mn, Pr and Sb.