JP2775808B2 - Method for producing ceramic screen ink - Google Patents

Description

The present invention relates to a multilayer ceramic capacitor, a multilayer ceramic substrate, a varistor, a piezoelectric element, a thick film capacitor, etc., which are widely used for electric products such as video tape recorders and liquid crystal televisions. The present invention relates to a method for producing a ceramic screen ink used when producing a ceramic electronic component by a screen printing method.

2. Description of the Related Art In recent years, in the field of electronic components, with the increase in the density of circuit boards, ceramic electronic components have been manufactured using a high-precision screen printing method.

First, a method for producing a screen ink will be briefly described. As a method of manufacturing a screen ink used for screen printing of ordinary commercial printing (poster printing, etc.),
A predetermined pigment powder is dispersed in a vehicle by shearing using a three roll or the like, and is manufactured as a screen ink (hereinafter, referred to as a general screen ink).

Further, similarly to the general screen ink, the ceramic screen ink used for manufacturing various ceramic electronic parts is also manufactured as a ceramic screen ink by dispersing ceramic powder in a vehicle by shearing using a three roll or the like. (Hereinafter, referred to as a conventional manufacturing method).

However, ceramic screen inks require very high ink properties as compared with general screen inks. In particular, the required properties from the ink surface include the degree of kneading of the ink. Here, the degree of kneading is the degree of dispersion when the powder and the vehicle are kneaded with a vehicle in an operation of converting the powder and the vehicle into an ink using a milling machine, and the powder and the vehicle are finely dispersed in the vehicle. This is one of the means for evaluation, which is defined in JIS (K-5701) so as to evaluate using a grind meter.
It is generally known that the degree of kneading can be increased by decomposing (or dispersing) secondary particles of powder in ink into primary particles.

Conventionally, when a ceramic electronic component is manufactured using a ceramic screen ink having poor kneading degree (a lot of secondary particles and poor dispersion), it is known that the reliability of the finished ceramic electronic component is poor. . If the kneading degree of the ceramic screen ink is poor (there is an uneven mass in the ceramic screen ink), voids (holes) and the like are generated inside the ceramic electronic component, so that the reliability is deteriorated. For this reason, in order to manufacture a highly reliable and highly accurate ceramic electronic component, it is indispensable to manufacture a ceramic screen ink having a higher degree of kneading than a general screen ink.

Generally, ceramic powder contains a large number of secondary particles that are firmly bonded (aggregated) by being calcined. When a ceramic powder containing a large number of such strongly bonded secondary particles is formed into an ink using a three-roll mill in the same manner as in the conventional production method, the kneading degree of the ink cannot be increased. It is considered that there was a limit in decomposing the strongly bonded secondary particles into primary particles. This is because it is difficult to obtain the ability to disperse these strong secondary particles to primary particles by the degree of shearing with a three-roll mill, and if the shearing conditions are strengthened in a three-roll mill, the secondary particles are reduced to the primary particles. Before dispersing,
This is because there is a problem that the resin contained in the vehicle is physically destroyed (such as a decrease in the molecular weight) and the physical properties of the resulting ink change (such as a decrease in viscosity).

Therefore, the wet method is widely used for dispersing the ceramic powder containing such strong secondary particles. Here, the wet method is a method of dispersing the ceramic powder together with a predetermined solvent and resin using a ball mill for several hours to several tens of hours. With a dispersion method using such a ball mill, a product having a high viscosity cannot be produced. This is because, when attempting to disperse a high-viscosity ceramic ink using a ball mill, a phenomenon occurs in which the ball cannot move due to its high viscosity and adheres to the inner wall of the ball mill or the like. . For this reason, it is usually difficult to produce a ceramic ink of about 30 poise or more with a disperser using balls, and a ceramic ink of 10 poise or less is usually produced with a disperser using balls such as a ball mill. . On the other hand, when used as a screen ink, if the viscosity is too low, it will ooze out of the screen, so that it needs to have a certain viscosity or more (about 100 poise or more, preferably about 500 poise). As described above, only a low-viscosity ink can be produced by the wet method using a ball, and there is a problem that the slurry thus produced cannot be used for screen printing.

It has also been proposed to add a resin after dispersing a ceramic powder in a solvent by a ball mill. However, when the ceramic ink is manufactured by a ball mill after adding the resin, the ball may not move due to the thickening action of the resin, so that the amount of the resin added is limited.

Problems to be Solved by the Invention In such a method for producing a ceramic screen ink, a ball mill could not be used because the viscosity was too high. Further, in the production method using a three-roll mill used in the production method of the usual screen ink, the ceramic powder could not be sufficiently dispersed.

In view of such problems, an object of the present invention is to produce an excellent ceramic screen ink having a high degree of kneading.

Means for Solving the Problems In order to solve this problem, the present invention relates to 100 parts by weight of the calcined ceramic powder, 10 parts by weight or more and 60 parts by weight or less of a solvent, and 0.1 part by weight or more and 2 parts by weight of a dispersant. Part below
After being dispersed with a dispersing machine using a rotary or vibrating ball, the mixture is filtered, and a resin is added to the filtrate.
An object of the present invention is to provide a method for producing a ceramic screen ink, which comprises kneading with a three-roll mill after reducing the pressure to 0000 poise or less.

Operation With this configuration, when the ceramic powder is dispersed in a solvent using a ball mill, the concentration of the ceramic powder can be set high by adding a dispersing agent, and the mixing of impurities such as ceramics with a ball can be suppressed. Increase the dispersion effect of the ceramic powder due to the impact or grinding of the ceramic powder, first disperse the ceramic powder in the form of primary particles in the solvent, then add the resin, make the viscosity 100 poise to 10,000 poise By dispersing the ceramic powder by a shearing motion using a three-roll mill, the kneading degree of the ink can be effectively increased.

That is, in the method for producing a ceramic screen ink of the present invention, secondary particles of fine ceramic powder are effectively pulverized by dispersing the secondary particles up to the primary particles in a low viscosity state in which no resin is added. Then, a resin is added to increase the viscosity, and the dispersed primary particles are stabilized in the resin without drying, thereby producing a ceramic screen ink having a kneading degree. That is, at the time of dispersion in a low-viscosity state, filtration is performed after the secondary particles formed by calcination of the ceramic particles are effectively broken down to the primary particles by using a dispersing machine using a ball effectively because of the low viscosity. Then, add a resin to the filtrate to a predetermined viscosity,
By kneading using a three-roll mill, the kneading degree of the ink can be increased without changing the molecular weight of the resin.

EXAMPLES Hereinafter, a method for producing the ceramic screen ink of the present invention will be described.

First, a ceramic screen ink produced by the production method of the present invention (hereinafter simply referred to as the invention method) and a ceramic screen ink produced by the conventional method (hereinafter simply referred to as the conventional method) were produced and compared.

First, the ceramic screen ink of the method of the present invention was produced as follows. First, 38 parts by weight of a solvent, 0.5 parts by weight of a dispersant, and 50 parts by weight of 2 mmφ zirconia balls are added to 100 parts by weight of a dielectric calcined powder containing barium titanate as a main component, and about 6 parts by using a vibration type ball mill. The slurry was dispersed for a time to obtain a slurry. Here, the viscosity of the slurry is measured using a double cylindrical rheometer composed of JIS standard viscosity liquid at a measurement temperature of 25 ° C. and a shear rate range of 10 to 500 (1 / sec). Met. Further, when the degree of dispersion (kneading degree) was evaluated using a grindometer, it was found that the particles were dispersed to approximately 1 μm or less and almost to primary particles. As a method of evaluating the degree of dispersion, a method according to a grindometer defined in JIS (K-5701) (0 to 10 μm
) Was prepared, and this was used to evaluate the degree of training. Further, at the same time, when the dielectric calcined powder was measured using a commercially available laser type particle size distribution meter, the average particle size was
1.2 microns. Here, as the dispersant,
Anionic, cationic, nonionic and amphoteric surfactants are widely used. In the present embodiment, among these, nonionic dispersants and polyethers are particularly used as dispersants for new ceramics. The system was selected and used.

Next, remove the zirconia beads from this slurry,
The slurry was filtered. Here, as a filter, a prefilter and a membrane filter having a pore size of 10 μm were used, and the mixture was filtered under pressure and the filtrate was added. Next, a butyral resin was added to the filtrate to give a viscosity of about 500 poise, and then the ink was made into an ink using a ceramic three-roll mill (hereinafter simply referred to as an inventive ink).

For comparison, the calcined barium titanate powder described above by a conventional method was screen-inked. this is,
First, a vehicle comprising butyral resin, additives and a solvent corresponding to the invention ink is manufactured, and then the calcined powder described above is added corresponding to the invention ink, and is converted into an ink using a three-roll mill (hereinafter simply referred to as a conventional ink). )did.

For further comparison, pure water was added to the calcined powder and dispersed for 100 hours using a ball mill.
What was evaporated in a drier heated to ° C was converted into an ink using a three-roll mill (hereinafter simply referred to as conventional ink).

Next, Table 1 shows the results of the kneading time of each ink with three rolls (inking time) and the degree of kneading of the ink at that time.

From the results shown in Table 1, it is understood that the inventive ink can improve the kneading degree in a shorter time than the conventional ink. Also,
With the conventional ink, it was found that secondary particles contained in the baked powder could not be sufficiently decomposed into primary particles by only three-roll mill dispersion. Further, in the conventional ink, it is considered that secondary particles which are relatively hard to be decomposed when pure water is evaporated after the baked powder is pulverized into primary particles by a wet method. Further, it was attempted to filter the conventional ink and the conventional ink using the membrane filter, but the filtration could not be performed. This is because the kneading degree of these inks is not sufficient.

In particular, in the method for producing a ceramic screen ink, since the viscosity at the time of filtration can be extremely low because no resin is added, the filtration can be easily performed.

In this example, three rolls made of ceramic were used. This is because when using a metal three-roll, there is a problem that the metal on the roll surface is shaved by the ceramic powder when kneading the ceramic powder, and consequently is mixed into the ink as an impurity. is there.

The dispersing machine used in the production of the ceramic screen ink may be any type using a ball, and may be a rotating ball such as a ball mill or a side mill, or a vibrating ball.

When the secondary particles contained in the calcined powder were decomposed into primary particles, a ball having a diameter of about 0.5 to 5 mm was effective.

The amount of the solvent added to the ceramic powder is 100 parts by weight of the ceramic powder, and if the solvent is not more than 10 parts by weight, the surface of the ceramic powder can be completely wetted with the solvent even if an additive is added, and dispersed by a ball mill. Since the required fluidity cannot be provided, the dispersion by the balls cannot be performed efficiently. Also, for 100 parts by weight of ceramic powder,
When the amount of the solvent exceeds 60 parts by weight, the concentration of the ceramic powder becomes low, and the efficiency of dispersion becomes poor.

Also, when kneading the ink using a three-roll mill, if the viscosity is less than 100 poise, the kneading effect by shearing in the three-roll mill is poor, while if it exceeds 10,000 poise, the viscosity is too high, During kneading, the ink slips on the surface of the three-roll mill, so that the kneading effect deteriorates.

Further, the addition amount of the dispersant was effective at 0.1 part by weight or more with respect to 100 parts by weight of the ceramic powder, and was particularly effective at 0.5 to 1 part by weight. If the amount exceeds 2 parts by weight, there is a problem in sinterability.

Further, after the ceramic screen ink according to the present production method is dispersed using a ball, it is easily filtered using a 5 μm membrane filter (if necessary, filtration using a pre-filter, and the remaining 5 μm It was possible to produce a ceramic screen ink from which particles having the above-mentioned particle diameter were completely removed, and thus to easily produce a ceramic screen ink composed of particles having a particle diameter smaller than a desired one.

In particular, in the case of ceramic screen inks used in the manufacture of electronic components, the particle size design of the ceramic powder contained therein depends on the filling ratio (clogging degree) of the dry ink film.
Is an important factor in raising For this reason, conventionally, ceramic particles having different particle diameters are mixed in a powder state and then formed into an ink. However, according to the present manufacturing method, after using a ceramic powder having a different particle size, a ball is dispersed using a disperser using a ball, and filtered,
By mixing this filtrate, a ceramic screen ink composed of particles having different particle diameters can be produced in a dispersed state. In this way, the ink properties, electrical properties,
The filling ratio and the like can be further improved.

Effect of the Invention As described above, the present invention is to disperse the calcined ceramic powder in a low viscosity state in which no resin is added by a dispersing device using a rotary or vibration ball in a solvent. Secondary particles can be easily broken down to primary particles,
Further, filtration can be easily performed, and a resin having high kneading degree can be easily produced by adding a resin to the filtrate after the filtration and kneading the ink using a three-roll mill.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Okuyama 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahiro Kato 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Satoshi Osan 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Takashi Iguchi 1006 Odaka, Kazuma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Katsuyuki Miura 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-84172 (JP, A) JP-A-63-260199 (JP, A) JP-A 63-84 232201 (JP, A) JP-A-2-208371 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09D 11/00-11/14 H01G 4/12 H05K 1/09

Claims (1)

(57) [Claims] 1. A solvent of 10 to 60 parts by weight and a dispersant of 0.1 to 2 parts by weight are added to 100 parts by weight of the calcined ceramic powder, and a rotary or vibrating ball is used. After being dispersed with a dispersing machine, the mixture was filtered, a resin was added to the filtrate, the viscosity was reduced to 100 poise to 10,000 poise, and then kneaded using a three-roll mill to produce a ceramic screen ink. Method.