JPH0656510A - Ceramic slurry composition - Google Patents

Abstract

PURPOSE:To provide a ceramic slurry compsn. capable of producing a ceramic green sheet having a low actual carbon ratio and high reliability. CONSTITUTION:Ceramic powder as starting material is mixed with a binder soln. to obtain the objective ceramic slurry compsn. The binder soln. contains a binder made of a polymer obtd. by copolymerizing at least one kind of monomer selected among alkyl methacrylates each having a 1-4C alkyl group with at least one kind of monomer selected among alkyl acryaltes or alkyl methacrylates each having a hydroxyl group added to the alkyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic slurry composition used for producing a ceramic green sheet, and more particularly to a binder in a binder solution used for slurrying a ceramic raw material powder.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for electronic parts such as monolithic ceramic capacitors to be lightweight and compact and to be low in price. And promoting further multi-layering,
In forming the internal electrodes, an inexpensive base metal material that replaces expensive Pt, Pd, Ag, or the like, for example, a conductive paste made of Ni or Cu having excellent high frequency characteristics is used. In addition, this type of conductive paste,
It is produced by mixing a predetermined base metal material and an organic solvent such as higher alcohol or turpentine oil.

The monolithic ceramic capacitor is generally manufactured by the following procedure. That is, first, a prepared ceramic raw material powder is prepared, and a binder solution having a required composition is added to the ceramic raw material powder and mixed to prepare a ceramic slurry composition. The binder solution used for making the slurry contains a binder whose main component is an acrylic resin.

Next, after the obtained ceramic slurry composition is formed into a sheet by a doctor blade method or the like,
A conductive paste to be internal electrodes is applied by screen printing on the surface of each of the formed ceramic green sheets. Further, a predetermined number of ceramic green sheets are stacked on each other to form a laminated body, and after the laminated body is subjected to binder removal processing, the binder removed-processed laminated body is fired in a high temperature atmosphere. After that, when necessary external electrodes are formed on the fired body thus obtained, a monolithic ceramic capacitor or the like is completed.

[0005]

By the way, when the internal electrodes are formed by using the base metal material, it is necessary to perform the binder removal processing and firing of the laminated body during the above-mentioned manufacturing procedure in a non-oxidizing atmosphere. In particular, when the conductive paste contains Cu as a main component, the firing temperature must be set low. That is, when a conductive paste containing a base metal material as a main component is heated at a high temperature in an oxygen-containing atmosphere, an oxide, which is a good quality insulator, is formed. It is fired in a non-oxidizing atmosphere to prevent it. However, when the laminated body is fired in a non-oxidizing atmosphere, the binder in the ceramic green sheet remains as carbon, and pores (pores) due to the presence of carbon are present in the fired body. Since it may remain, a characteristic inconvenience occurs in the manufactured electronic component.

The acrylic resin binder is used in the ceramic green sheet because the binder can cause depolymerization (a chemical reaction in which the polymer decomposes into a monomer) even at a low temperature. This is because it is believed that the carbon residual rate (hereinafter referred to as the residual carbon rate) in the can be reduced. However, when forming the internal electrodes of the above-mentioned multilayer ceramic capacitor, it is common to apply a conductive paste on the ceramic green sheet, and in such a case, the conductive paste is included in the conductive paste. The organic solvent may penetrate into the ceramic green sheet and dissolve the acrylic resin binder. Therefore, the thinner the thickness of the ceramic green sheet, the more the reliability of the ceramic green sheet is impaired due to the attack of the organic solvent.

The present invention was devised in view of such inconvenience, and an object thereof is to provide a ceramic slurry composition capable of producing a highly reliable ceramic green sheet having a low residual carbon rate. There is.

[0008]

A ceramic slurry composition according to the present invention comprises a mixture of a ceramic raw material powder and a binder solution, wherein the binder solution contains an alkyl group having 1 to 4 carbon atoms. Having at least one monomer selected from the group consisting of methacrylic acid alkyl esters (hereinafter referred to as “monomer”) and selected from the group consisting of acrylic acid alkyl esters in which a hydroxyl group is added to an alkyl group or methacrylic acid alkyl esters It is characterized in that it contains a binder made of a polymer obtained by copolymerizing at least one kind of the obtained monomer.

[0009]

EXAMPLES The ceramic slurry composition according to the present invention will be described below. That is, this ceramic slurry composition is used for producing a laminated ceramic capacitor or the like in which internal electrodes made of a base metal material such as Ni or Cu are formed and which is to be fired in a non-oxidizing atmosphere. The ceramic green sheet is prepared by mixing the ceramic raw material powder and the binder solution into a slurry.

First, the ceramic raw material powder in this embodiment is composed of barium carbonate (BaCO ₃ ) and titanium oxide (Ti).
O ₂ ) as a starting material, was wet-mixed using a ball mill, dehydrated and dried, then calcined at a temperature of 1100 ° C. for 2 hours and then pulverized. On the other hand, the binder solution for slurrying the ceramic raw material powder contains a binder having a required composition, and the binder has 1 to 4 carbon atoms.
At least one monomer selected from the group consisting of methacrylic acid alkyl esters having an alkyl group, and at least one selected from the group consisting of acrylic acid alkyl esters in which a hydroxyl group is added to an alkyl group or methacrylic acid alkyl esters It is composed of a polymer obtained by copolymerizing the above monomer.

That is, the alkyl group of the methacrylic acid alkyl ester may be a single or a plurality of combinations from a methyl group having 1 carbon atom to i (iso)-or n (normal) -butyl having 4 carbon atoms. The hydroxyl group-added acrylic acid alkyl ester or methacrylic acid alkyl ester may be any one in which one or more hydroxyl groups are added to the alkyl group. At this time, since the hydroxyl group is added, the binder having the above structure cannot be dissolved by the higher alcohol or turpentine oil which is the organic solvent contained in the conductive paste. Incidentally, it is needless to say that the hydrophilicity increases as the introduction ratio of the hydroxyl group increases, and the hydrophobicity increases as the introduction ratio decreases, and the introduction ratio of the hydroxyl group depends on the content of the conductive paste used for forming the internal electrode. It will be adjusted according to the organic solvent.

Further, at this time, in the copolymerization for obtaining the polymer, after charging 500 g of toluene and 100 g of isopropyl alcohol into a 2 L separable flask equipped with a reflux cooling device, the temperature was raised to 80 ° C. , N-butyl methacrylate 300 g, methyl methacrylate 200 g, 2-hydroxyethyl acrylate (HOA)
Polymerization is performed by adding 100 g and 5 g of benzoyl peroxide dropwise over several hours. Then, the polymer obtained by the copolymerization is cooled and then diluted with toluene to adjust the solid content concentration to about 50%, whereby a binder solution is obtained.

Next, 100 of the above ceramic raw material powder is used.
2 parts by weight of the above binder solution (solid content concentration 50%)
6 parts by weight, 2 parts by weight of ethylene glycol (molecular weight 950 to 1050) which is a plasticizer, 40 parts by weight of toluene, and 20 parts by weight of methyl ethyl ketone were put in a ball mill together with a cobblestone made of zirconia and having a diameter of about 5 mm. By wet mixing for 15 hours, a slurry-like ceramic slurry composition is obtained.
Then, the obtained ceramic slurry composition is formed into a sheet by a doctor blade method or the like to produce a ceramic green sheet having a thickness of about 50 μm.

Further, the ceramic green sheet thus prepared is punched into a rectangular shape having a size of 50 mm × 70 mm to prepare a sample for a solvent resistance test and a static electricity generation test. The solvent resistance test is a test for examining a change in sheet shape by immersing a punched sheet in a higher alcohol which is an organic solvent for a conductive paste, and the static electricity generation test is 2 The punched sheets are brought into contact with each other in an area of about half each, and the difficulty of sticking (sticking state) between the punched sheets is determined based on static electricity generated when the sheets are peeled off.

After that, a predetermined number of punched sheets are stacked and thermocompression bonded to produce a laminated element body having a thickness of about 1 mm, and the laminated element body is further formed into rectangular parallelepiped shapes of about 10 mm square. A sample for a residual coal rate test is prepared by dividing. The residual coal rate test is a test in which the ratio of carbon remaining in the sample is examined by a residual coal rate meter (for example, EMIA-511 manufactured by Horiba Ltd.), and the 250 ° C residual coal rate is 250. The test results for the sample left for 12 hours in the air of 800 ° C. and the 800 ° C. residual coal rate mean the test results for the sample heated in the nitrogen gas atmosphere of 800 ° C. for 5 hours.

Separately from the above procedure, a binder made of an acrylic resin as in the conventional example and a binder made of polyvinyl acetal obtained by acetalizing polyvinyl alcohol (acetalization degree: 65 mol%) are prepared. After making a ceramic slurry composition using each of them into a sheet by following the same procedure as above, a sample for solvent resistance test, static electricity generation test and residual coal rate test made of these ceramic green sheets is prepared respectively. To do. In the following description, a sample made of the ceramic slurry composition according to the present example is referred to as an example product, while a sample made of a ceramic slurry composition prepared using an acrylic resin binder is referred to as a conventional example product 1, A sample made of a ceramic slurry composition prepared by using a polyvinyl acetal binder is referred to as Conventional Example Product 2.

Then, a solvent resistance test, a static electricity generation test and a residual coal rate test were carried out on each of the example product and the conventional product 1 and 2 obtained as described above.
The results shown in Table 1 were obtained. For the judgment results in the solvent resistance test and static electricity generation test, ○,
In the solvent resistance test, the shape of the punched sheet does not change, and the changed shape is indicated by x, while in the static electricity generation test, the sticking due to static electricity is clearly indicated by x, and the other is not indicated. ○

[0018]

[Table 1]

According to Table 1, in the case of the conventional product 1 using the acrylic resin binder, the shape change of the punched sheet and the occurrence of sticking due to static electricity are observed, while in the embodiment product and the conventional product 2, good results are obtained. It can be seen that the solvent resistance is obtained and the occurrence of sticking due to static electricity is small. Further, it can be seen that, in the example product and the conventional example product 1, the excellent residual carbon rates which are substantially equal to each other are obtained, whereas in the conventional example 2 using the polyvinyl acetal binder, the residual carbon rate is increased.

That is, according to these test results, the conventional example product 1 is susceptible to attack by the conductive paste despite the low residual carbon rate, and moreover, static electricity is easily generated. Although the example product 2 has a high residual carbon rate in spite of being less susceptible to attack, the ceramic slurry composition as an example product has a low residual carbon rate and is less susceptible to attack by the conductive paste. It has been clarified that sticking due to static electricity is less likely to occur. Incidentally, the static electricity in the solvent-based ceramic slurry composition causes a problem in processing as the sheet thickness becomes thinner, and also serves as an ignition source for solvent explosion.
With the ceramic slurry composition according to this example, it is extremely important that the generation of static electricity is suppressed.

[0021]

As described above, when a ceramic green sheet is produced using the ceramic slurry composition according to the present invention, the residual coal rate in this ceramic green sheet is lowered and the reliability is improved. become. Therefore, even if the ceramic laminated body is fired in a non-oxidizing atmosphere because of the necessity of forming the internal electrodes using a conductive paste made of a base metal material, the pores due to the presence of carbon are present in the fired body. Therefore, it is possible to obtain an effect that the characteristic inconvenience in the electronic component does not occur.

Claims (1)

[Claims] 1. A ceramic slurry composition prepared by mixing a ceramic raw material powder and a binder solution, wherein the binder solution is selected from the group consisting of alkyl methacrylic acid esters having an alkyl group having 1 to 4 carbon atoms. From a polymer obtained by copolymerizing at least one monomer selected from the group consisting of alkyl acrylate or methacrylic acid alkyl ester in which a hydroxyl group is added to an alkyl group A ceramic slurry composition comprising the following binder.