JP2002015843A - Manufacturing method for ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a ceramic heater, capable of favorably manufacturing a mold for the ceramic heater by preventing the aggregation of alumina particles, even if the average particle size of alumina particles of a raw material of the ceramic heater is made small. SOLUTION: A binder of 10-30 pts.wt., a solvent of 4-14 pts.wt., and a plasticizer of 3-10 pts.wt. are added to particles mainly comprising alumina of 100 pts.wt., and 0.007-0.2 g dispersant made of a phosphate per m2 of the surface area of the alumina particles is mixed to the mixture to prepare a mixed composition, and the mixed composition is used to manufacture the mold for the ceramic heater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a ceramic heater in which a resistance heating element is embedded in ceramic.

[0002]

2. Description of the Related Art A rod-shaped ceramic heater in which a resistance heating element made of a high melting point metal is buried between a core material and an insulating layer wrapping the core material is used in an oxygen sensor for automobiles and a glow system. It is widely used as a heat source and as a heat source for oil vaporizers such as semiconductor heaters and oil fan heaters.

FIG. 8A is a cross-sectional view schematically showing a part of a process of manufacturing such a ceramic heater, and FIG. 8B is a front view.

As shown in FIG. 1, first, a conductive paste layer 53 serving as a resistance heating element is formed on a plastic film 51 having releasability and dried, and then the entire conductive paste layer 53 is removed. A paste for an insulating layer containing alumina particles, a binder resin and a solvent is overlaid and printed so as to cover the layer, a layer of the green sheet 52 is formed, and the green sheet 52 is dried.

Next, a through-hole 56 for a through-hole is formed near the end of the green sheet 52, and the through-hole 56 for the through-hole is filled with a conductive paste, and the through-hole 56 for a through-hole filled with the conductive paste is formed. A paste layer 54 for external terminals is formed using a tungsten paste.

[0008] Thereafter, although not shown in FIG. 8, the laminate 50 is turned over so that the green sheet 52 is on the lower side, and a cylindrical core material compact is placed on the laminate 50. Then, the laminate 50 is wound around the core material compact to complete the production of the heater compact. Thereafter, the ceramic heater having the configuration described below is manufactured by performing degreasing, firing, and the like on the molded body for a heater.

FIG. 9A is a perspective view schematically showing an example of a ceramic heater obtained by the above-described process, and FIG. 9B is a sectional view taken along line AA in FIG. 9A.

As shown in FIG. 9 (a), in the ceramic heater 30, a resistance heating element 33 is provided on the surface of a cylindrical core material 31, and the insulation is provided so as to cover the entire resistance heating element 33. A layer 32 is formed.

The resistance heating element 33 comprises a heating section 33a and a non-heating section 33b formed for connection to a power supply.
The heat generating portion 33a is formed by repeatedly forming a U-shaped pattern and an inverted U-shaped pattern in the left-right direction in the circumferential direction.

The non-heat generating portion 33b is connected to an external terminal 34 provided outside the insulating layer 32 via a through hole (not shown) or the like. The external terminal 34 is connected to an oxygen sensor device or the like. By being fitted into the connection terminal portion, it is connected to a power supply or the like. When the resistance heating element 33 is energized through the external terminals 34 and the like, the heating section 33a generates heat, so that it functions as a heater.

[0011] The ceramic heater having the above-described structure is required not only to reach a target temperature in a short period of time, but also to have excellent durability. From the viewpoint of prevention, those having excellent mechanical properties such as bending strength are required.

[0012]

In order to meet the above-mentioned requirements, methods for improving the mechanical properties such as the bending strength of a ceramic heater have been studied. It is considered that the particle size is smaller than that currently used.

However, when an attempt is made to produce a green sheet for a molded article using alumina particles having a small average particle size, the alumina particles contained in the green sheet aggregate with each other, and a predetermined shape is formed on the plastic film. However, there is a problem that the green sheet cannot be formed.

The present invention has been made in view of the above-mentioned problems, and since the alumina particles do not agglomerate even if the average particle size of the alumina particles as the raw material for the ceramic heater is reduced, the green sheet for the ceramic heater can be satisfactorily prepared. It is an object to provide a method for manufacturing a ceramic heater that can be manufactured.

[0015]

According to the present invention, a binder is used in an amount of 10 to 30 parts by weight, a solvent is used in an amount of 4 to 14 parts by weight, and a plasticizer is used in an amount of 100 parts by weight of particles mainly composed of alumina.
After adding a dispersant composed of a phosphate ester salt in an amount of 0.007 to 0.2 g per 1 m ² of the surface area of the alumina particles, a mixed composition was prepared. A method for manufacturing a ceramic heater, comprising forming a molded body for a ceramic heater using the composition. Hereinafter, the present invention will be described in detail.

[0016]

First, a method for manufacturing a ceramic heater according to the present invention will be described. In the mixed composition used in the present invention, the binder is 10 to 30 parts by weight, and the solvent is 4-1 to 100 parts by weight of particles mainly composed of alumina.
Prepared by adding 4 parts by weight and a plasticizer in a ratio of 3 to 10 parts by weight, and further mixing 0.007 to 0.2 g of a dispersant composed of a phosphate salt per 1 m ² of the surface area of the alumina particles. I do.

In the method for manufacturing a ceramic heater of the present invention, as described below, in order to prepare a molded body for a heater, a molded body for a core material serving as a core material and a green sheet serving as an insulating layer are used. At this time, a molded body for a core material and a green sheet are produced using the mixed composition having the above composition, and a molded body for a heater is produced by combining these.

The average particle size of the alumina particles used in preparing the above mixed composition is preferably 1 to 10 μm, and 2 to 5 μm.
Is more preferred. If it exceeds 10 μm, the mechanical properties such as bending strength of the ceramic heater to be manufactured become poor. It is easy to occur. The average particle size of the alumina particles is most preferably 3 to 4 μm. The term “particles mainly composed of alumina” is used because, in addition to alumina particles, sintering aids such as silica, MgO, and CaO are usually contained.

The binder is not particularly limited.
For example, polyvinyl alcohol, methylcellulose, ethylcellulose, carboxycellulose, an acrylic binder and the like can be mentioned.

The solvent is not particularly restricted but includes, for example, α-terpineol, glycol and the like.

The plasticizer is not particularly restricted but includes, for example, phthalic esters.

As the dispersant, a surfactant comprising a phosphate salt is used. Examples of the phosphate salt include polyoxyethylene alkyl ether phosphate, polyoxyethylene alkylphenyl ether phosphate, and alkyl phosphate.

Examples of the polyoxyethylene alkylphenyl ether phosphate include a monoester having a chemical structure represented by the following formula (1) and a diester having a chemical structure represented by the following formula (2). .

[0024]

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[0025]

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In the above formula, a nonyl group is bonded as an alkyl group, but the alkyl group is not limited to the above nonyl group, and any other alkyl group having 4 to 12 carbon atoms may be used. The compound may be a monoester, a diester, or a triester. Further, the alkyl group may be linear or have a side chain.

The polyoxyethylene alkyl ether phosphate is a compound represented by the formula (1) or (2) in which an alkyl group is bonded instead of the nonylphenyl group. Having 4 to 1 carbon atoms
2 can be mentioned. Further, the alkyl group is
It may be linear or have a side chain. further,
The compound may be a monoester, a diester or a triester.

In the above alkyl phosphate, an alkoxyl group is bonded to phosphoric acid, and the above compound may be a monoester, a diester or a triester. The alkoxyl group has 4 to 4 carbon atoms.
Twelve can be mentioned. Further, such an alkoxyl group may be linear or have a side chain.

The binder is added in an amount of 10 to 30 parts by weight based on 100 parts by weight of particles mainly composed of alumina. When the amount exceeds 30 parts by weight, the amount of the binder is too large, so that the shrinkage increases in the firing step and cracks and the like are easily generated. On the other hand, when the amount is less than 10 parts by weight,
The bonding force between the alumina particles and other additives cannot be sufficiently ensured, and it becomes difficult to produce a core material compact or a green sheet.

The solvent is added in an amount of 4 to 14 parts by weight based on 100 parts by weight of particles mainly composed of alumina. If the amount is more than 14 parts by weight or less than 4 parts by weight, it becomes difficult to produce a green sheet or a molded body for a core material using the mixed composition.

The plasticizer is added in an amount of 3 to 10 parts by weight based on 100 parts by weight of particles mainly composed of alumina. If the amount exceeds 10 parts by weight, the density of the entire molded body for a heater decreases, so that the amount of shrinkage increases during sintering and cracks are easily generated. In addition, cracks also occur during drying and degreasing of the molded body. More likely to occur. Also,
When the amount of the plasticizer is less than 3 parts by weight, it becomes difficult to produce a core material molded article or a green sheet.

The above-mentioned dispersant has a surface area of 1 m of the alumina particles.
0.007 to 0.2 g is added to ² . 0.2
If the amount exceeds g, the density of the molded body for a heater decreases, so that the amount of shrinkage during sintering increases and cracks easily occur.Also, when the molded body is dried or degreased, cracks are easily generated. Become. On the other hand, if it is less than 0.007 g, the alumina particles in the mixed composition are aggregated,
It becomes difficult to produce a green sheet or a molded body for a core material.

Although the amount of the dispersant added increases as the average particle size of the alumina particles decreases, the specific surface area increases. However, in practice, it is desirable to add the dispersant in an amount larger than the rate at which the specific surface area increases. That is, for example, when the average particle diameter of the alumina particles is between 2 and 5 μm,
If the average particle size of the alumina particles is smaller, the amount of the dispersant added is set to be larger than the rate of increase in the specific surface area. It is desirable to set the addition amount so that when the average particle diameter of the alumina particles approaches ² to 3 μm, the addition amount approaches 0.2 g per 1 m ² of the surface area of the alumina particles.

This is because the average particle size of the alumina particles decreases, the surface area increases, the alumina particles in the mixed composition become unstable, and the degree of aggregation tends to increase. This is because a larger amount of a dispersant is required in order to produce a green sheet or core molding having good characteristics in which particles are stably dispersed.

1 to 4 are cross-sectional views schematically showing a part of the manufacturing process of the ceramic heater 10 using the above-mentioned mixed composition. In each of the drawings, (a) is a cross-sectional view,
(B) is a front view.

In the present invention, after the mixed composition is prepared in this manner, first, as shown in FIG. 1, a green sheet 25 for an adhesive layer serving as an adhesive layer 15 is formed on a plastic film 27 having releasability. Then, a conductive paste layer 23 serving as a heating portion of the resistance heating element 13 and a conductor paste layer 24 serving as a non-heating portion are formed. As shown in FIG. 1, the adhesive layer green sheet 25 has a slope having a constant gradient.

The conductive paste layers 23 and 24 desirably contain at least one selected from the group consisting of high melting point metals of W, Re and Mo, a ceramic component such as alumina, a binder resin and a solvent.

Next, as shown in FIG. 2, the green sheet 22 serving as the insulating layer 12 is formed using the above-mentioned mixed composition so as to cover the entire conductive paste layer 23 and a part of the conductive paste layer 24. Form a layer. Green sheet for adhesive layer 2
5 also has a composition similar to that of the green sheet 22 to be the insulating layer 12.

Thereafter, as shown in FIG. 3, the laminate 20 shown in FIG. 2 is turned over so that the green sheet 22 is on the lower side, and is placed on a predetermined table 26. The plastic film 27 is peeled off by being fixed to the table 26 by using air suction force or the like through a through hole (not shown) formed in the table 26.

Subsequently, as shown in FIG.
Of the core material, and the laminated body 20 is wound around the formed shape body 21 to produce a heater formed body. The molded body for a core material may also be produced by using the mixed composition.

Thereafter, in the presence of oxygen, at 400 to 600 ° C.
To remove organic substances in the core material molded body 28, the conductive paste layers 23 and 24, the adhesive layer green sheet 25, and the green sheet 24, and then calcination to obtain alumina or a high melting point. The ceramic heater 10 is manufactured by sintering a metal or the like. The firing temperature is 145
0 to 1650 ° C. is preferable, and the firing time is 0.5 to 12 ° C.
Time is preferred.

By making the formed body 28 hollow, the gas generated in the degreasing step and the sintering step can be released well, and the degreasing and sintering can be performed efficiently.

In the present invention, by using a mixed composition having such a composition, it is possible to produce a molded product for a core material and a green sheet having good characteristics even when alumina particles having a small particle size are used. Therefore, a ceramic heater having excellent mechanical properties and high strength can be manufactured.

FIG. 5A is a perspective view schematically showing an example of a ceramic heater manufactured by the above manufacturing method, and FIG. 5B is a sectional view taken along line AA in FIG. . FIG. 6 is a developed view in which a resistance heating element formed on a core material is developed on a plane.

As shown in FIG. 5, this ceramic heater 10 has a resistance heating element 1 on the surface of a cylindrical core material 11.
3 is provided, and an insulating layer 12 containing alumina as a main component and surrounding the core material 11 is formed so as to cover the entire resistance heating element 13.

The resistance heating element 13 is, as shown in FIG.
It is composed of a non-heat generating portion 13b and a heat generating portion 13a. The non-heat generating portion 13b is formed of a plurality of lines formed in parallel to reduce resistance and prevent heat generation.

As shown in FIG. 5, no insulating layer 12 is formed at one end of the ceramic heater 10, and an external terminal 14 extended from the resistance heating element 13 is provided at this portion. It is exposed. In a portion where the external terminal 14 is exposed, a considerably thick adhesive layer 15 is formed between the external terminal 14 and the core material 11, and the portion where the external terminal 14 is formed and the surface of the insulating layer 12 are substantially It is the same height.

In the ceramic heater 10 shown in FIG. 5, the external terminals 14 are exposed at the ends, but the ceramic heater manufactured by the manufacturing method of the present invention comprises a core made of ceramic and a core made of ceramic. The configuration is not limited to the above configuration as long as the resistance heating element is buried between the insulating layer made of ceramic to be wrapped.

Accordingly, as shown in FIG. 7, a notch 45 is formed at the end of the ceramic heater 40, and a part of the resistance heating element 43 (the non-heat generating portion 13b) is formed by the notch 4.
5, the exposed non-heat generating portion 13b
The lead wire 46 may be connected and fixed via a brazing material or the like. Further, a ceramic heater having a configuration as shown in FIG. 9 may be used.

FIG. 7 (b) shows a cross section of the axial component 130 of the resistance heating element 13 formed on the core material 11. As shown in FIG. The axial components 130 are arranged on the outer peripheral portion of the core material 11 at substantially equal intervals. This is the same for the ceramic heater 10 shown in FIG.

As described above, the axial component 130 is combined with the core material 11.
By arranging them at equal intervals on the outer peripheral portion of the heater, the objects to be heated around the ceramic heaters 10 and 40 can be heated to a uniform temperature.

Core 1 constituting this ceramic heater
No. 1 is composed mainly of alumina and SiO 2 as a sintering aid.
_{2 up} to 4% by weight, MgO up to 0.5% by weight, CaO
Is 1.2% by weight or less, and the density ratio of this ceramic substrate is 9%.
6% or more is preferable.

If the density ratio of the alumina ceramic constituting the core material 11 is less than 96%, or if the amount of the sintering aid is larger than the above range, the possibility that pores are present increases. The grain boundaries of the alumina ceramic constituting the aluminum alloy deteriorate due to migration or the like, and holes are easily formed.
Is easily oxidized. The density ratio is a percentage of the ratio of the density of the actual sintered body to the theoretical density of the ceramic.

The resistance heating element 13 is composed of W, Ta, Nb, T
It is desirable to be made of a high melting point metal such as i, Mo, and Re. These refractory metals may be used alone or in combination of two or more. Further, the resistance heating element 13 may be formed by adding a ceramic such as alumina to these.

The ceramic heater manufactured by the above-described manufacturing method is not only excellent in functional characteristics such as reaching a target temperature in a short time and excellent in durability, but also when manufacturing a molded body. In the mixed composition, since the dispersant composed of a phosphate ester salt is added in the above range, even if the average particle size of the alumina particles is reduced, the alumina particles are not aggregated with each other, and are good. Then, a molded body for a ceramic heater can be produced. Therefore, a ceramic heater having excellent mechanical properties such as bending strength can be manufactured.

[0056]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 First, particles mainly composed of alumina (average particle size of 3.2
μm (specific surface area 3.5m ^Two / Cm^Three )) 100 parts by weight,
Methacrylate ester-based copolymer 2 as a binder
2 parts by weight, as a solvent, 7.5 parts by weight of α-terpineol
Parts, 6.8 parts by weight of phthalic ester as a plasticizer
And the surface area of the alumina particles is 1 m^Two Against
(1) Polyoxynonyl phenyl ether represented by the formula
(Monoester) and polyoxy group shown in formula (2)
Nonylphenyl ether phosphate (diester)
Dispersant mixed at a ratio of 6: 4 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
0.094 g (8.22 weight) of Plysurf A212E
Parts) were mixed to prepare a mixed composition.

Next, using the method described in the above embodiment, a green sheet and a molded body for a core material and the like are prepared using the above-mentioned mixed composition, and the steps of degreasing and firing are performed. Ceramic heater 10 of the configuration shown
Was manufactured. The firing temperature at this time was 1600 ° C. Further, the resistance heating element 13 of the manufactured ceramic heater 10 contained 80% by weight of W, 17% by weight of Re, and 3% by weight of alumina. The thickness of the insulating layer 12 was 200 μm.

The resulting ceramic heater 10 was subjected to a three-point bending test to determine the bending strength. As a result, a high value of 190 N was shown.

Example 2 The composition of the mixed composition prepared in Example 1 was changed to particles mainly composed of alumina (average particle size of 3.8 μm (specific surface area of 2.10 μm).
0 m ² / cm ³ )) 100 parts by weight, as a binder,
Methacrylate copolymer 20.5 parts by weight, as a solvent, alpha-terpineol 9.0 parts by weight of phthalic acid ester 6.8 parts by weight contain as a plasticizer, and further, of the surface area 1 m ² of the alumina particles Dispersant similar to that used in Example 1: 0.0082 g (0.41 parts by weight)
In the same manner as in Example 1, a green sheet, a molded body for a core material, and the like were produced using the above mixed composition, and a ceramic heater was produced.

For the obtained ceramic heater, 3
A point bending test was performed to determine the bending strength. As a result, 18
It showed a high value of 0N.

Example 3 The composition of the mixed composition prepared in Example 1 was changed to particles mainly composed of alumina (average particle diameter 3.6 μm (specific surface area 2.
9 m ² / cm ³ )) 100 parts by weight, as a binder,
Methacrylic acid ester copolymer 22 parts by weight, as a solvent, alpha-terpineol 7.5 parts by weight of phthalic acid ester 6.8 parts by weight contain as a plasticizer, and further, of the surface area 1 m ² of the alumina particles, implemented The same dispersing agent as used in Example 1 was used, except that 0.11 g (8.22 parts by weight) was added and adjusted, and a green sheet and a core were prepared using the above mixed composition in the same manner as in Example 1. A molded body for a material was produced, and a ceramic heater was produced.

For the obtained ceramic heater, 3
A point bending test was performed to determine the bending strength. As a result, 18
It showed a high value of 5N.

Comparative Example 1 The composition of the mixed composition prepared in Example 1 was changed to particles mainly composed of alumina (average particle size of 3.2 μm (specific surface area of 3.2 μm).
5 m ² / cm ³ )) as a binder, 22 parts by weight of a methacrylate copolymer as a binder, 7.5 parts by weight of α-terpineol as a solvent, and 6.8 of phthalate as a plasticizer. Parts by weight, and based on 1 m ² of the surface area of the alumina particles, the same dispersant as used in Example 1: 0.0047 g (0.41 g)
In the same manner as in Example 1, an attempt was made to produce a green sheet using the above-mentioned mixed composition, except that the composition was adjusted by the addition of (parts by weight).

However, when a green sheet was prepared using the mixed composition prepared in Comparative Example 1,
Alumina particles in the printed mixed composition agglomerated, and a green sheet having a predetermined shape could not be produced.

As is evident from the results shown in Examples 1 to 3 and Comparative Example 1, the dispersant consisting of a phosphate ester salt was added to the surface area of 1 m ^{2 of the} alumina particles contained in the mixed composition. By adding 007 to 0.2 g, even if the average particle size of the alumina particles in the mixed composition was reduced, the alumina particles were uniformly dispersed, so that a good ceramic heater could be manufactured. In addition, the bending strength of the ceramic heater manufactured by reducing the average particle size of the alumina particles contained in the mixed composition was high.

[0067]

The method for producing a ceramic heater according to the present invention is as described above. Therefore, even if the average particle size of the alumina particles contained in the mixed composition used for the molded body for the ceramic heater is small, the ceramic heater can be used. A compact for a ceramic heater can be favorably produced without particles aggregating. In addition, a ceramic heater manufactured using such a molded body for a ceramic heater has excellent mechanical properties such as bending strength.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically showing one step in manufacturing a ceramic heater of the present invention, and FIG.
Is a front view.

FIG. 2A is a cross-sectional view schematically showing one step in manufacturing the ceramic heater of the present invention, and FIG.
Is a front view.

FIG. 3A is a cross-sectional view schematically showing one step in manufacturing the ceramic heater of the present invention, and FIG.
Is a front view.

FIG. 4A is a cross-sectional view schematically showing one step in manufacturing the ceramic heater of the present invention, and FIG.
Is a front view.

FIG. 5A is a perspective view showing an example of a ceramic heater according to the present invention, and FIG. 5B is a sectional view taken along line AA of FIG.

FIG. 6 is a developed view in which a resistance heating element constituting the ceramic heater of the present invention is developed in a plane.

FIG. 7A is a perspective view showing another example of the ceramic heater of the present invention, and FIG. 7B is a sectional view thereof.

FIG. 8A is a cross-sectional view schematically showing one step in manufacturing a conventional ceramic heater, and FIG.
Is a front view.

FIG. 9A is a perspective view showing a structure of a conventional ceramic heater, and FIG. 9B is a sectional view thereof.

[Explanation of symbols]

 10, 40 Ceramic heater 11, 41 Core material 12, 42 Insulating layer 13, 43 Resistance heating element 13a Heating portion 13b Non-heating portion 130 Axial component 131 Circumferential component 14 External terminal 15 Adhesive layer 45 Cutout portion 46 Lead wire

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K092 QA01 QA10 QB02 QB31 QB45 QB74 QB76 QC27 QC38 RA02 RB05 RB22 RD09 RD16 RD25 RF02 RF11 RF17 RF22 VV08 VV31 VV34 4G030 AA36 BA12 CA08 GA14 GA15 GA16 GA17

Claims (1)

[Claims] 1. A binder comprising 10 to 30 parts by weight of a binder, 4 to 14 parts by weight of a solvent, and 3 to 10 parts by weight of a plasticizer, based on 100 parts by weight of particles mainly composed of alumina. Per 1m ² of surface area of alumina particles,
0.007 to 0.2 of a dispersant comprising a phosphate ester salt
A method for manufacturing a ceramic heater, comprising: preparing a molded body for a ceramic heater by using the mixed composition after preparing a mixed composition by mixing g.