JP2001030227A - Preparations of ceramic slurry and ceramic green sheet and manufacture of laminated ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing ceramic slurry which enables uniform dispersion of ceramic powder without inflicting an excessive damage on the ceramic powder and enables efficient preparation of the ceramic slurry suitable for the use for manufacturing a ceramic electronic component, a method for preparing a ceramic green sheet and a method for manufacturing a laminated ceramic electronic component. SOLUTION: Mixed slurry of ceramic powder having a mean particle size of 0.01-1 μm and a dispersion medium is pressurized 32 with a high pressure and passed through a prescribed passage 33 in the condition that the maximum shear stress of 1000 [Pa] or above can be given to the ceramic powder. Thereby a shear force necessary for dispersion is exerted on the ceramic powder, without inflicting a large damage thereon, on the occasion when the mixed slurry passes through the passage 33, and thereby the ceramic powder is dispersed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic slurry and a ceramic green sheet used for manufacturing a multilayer ceramic electronic component, and a method for manufacturing a multilayer ceramic electronic component.

[0002]

2. Description of the Related Art A multilayer ceramic electronic component such as a multilayer ceramic capacitor or a ceramic multilayer substrate is usually manufactured through a process of laminating and pressing a ceramic green sheet, heat-treating and sintering a ceramic or an electrode.

For example, as shown in FIG. 6, an internal electrode 2 is provided in a ceramic element 1, and both ends of the ceramic element 1 are connected to the internal electrodes 2 alternately drawn to different end faces. A pair of external electrodes 3 so as to be conductive
When manufacturing a multilayer ceramic capacitor having a structure in which a and 3b are provided, it is usually manufactured by the following method.

[0004] First, an electrode arrangement sheet 11 (FIG. 7) is formed by disposing an internal electrode for forming a capacitance on a ceramic green sheet. Next, as shown in FIG. 7, a predetermined number of electrode-provided sheets 11 are laminated, and a ceramic green sheet (outer layer sheet) 21 having no electrodes disposed on both upper and lower surfaces thereof.
Are laminated and crimped to form a laminated body (laminated crimped body) in which one end side of each internal electrode 2 is alternately drawn to an end face on a different side. Then, after firing the laminated pressure-bonded body under predetermined conditions to sinter the ceramic, a conductive paste is applied to both ends of the fired laminated body (ceramic element) 1 (FIG. 6) and baked. External electrodes 3a and 3b (FIG. 6) which are electrically connected to the internal electrodes 2 are formed. Thus, a multilayer ceramic capacitor as shown in FIG. 6 is obtained.

[0005] Other multilayer ceramic electronic components such as a multilayer ceramic multilayer substrate are also manufactured through a process of laminating ceramic green sheets.

In general, ceramic green sheets used in the production of multilayer ceramic electronic components are prepared by mixing a ceramic powder with a dispersion medium (solvent), a dispersant, a binder, a plasticizer, and the like at a predetermined ratio, and using a bead mill or a ball mill. The ceramic slurry manufactured by mixing and dispersing using a medium type disperser such as an attritor, a paint shaker, a sand mill, etc., is formed into a sheet of a predetermined thickness by a method such as a doctor blade method, and then dried. Being manufactured.

However, in recent years, various multilayer ceramic electronic components such as multilayer ceramic capacitors have been reduced in size and size as in the case of other electronic elements.
Higher performance is required. For that purpose, it is necessary to reduce the thickness of the ceramic green sheet used for manufacturing the multilayer ceramic electronic component. In recent years, it has become necessary to use an extremely thin ceramic green sheet having a thickness of 10 μm or less.

As described above, in order to manufacture a ceramic green sheet having a small thickness, it is necessary to use, as a ceramic slurry used for manufacturing the ceramic green sheet, a slurry in which ceramic raw material powder is sufficiently dispersed. Therefore, it is necessary to use a fine powder ceramic raw material having an average particle size of about 0.01 to 1 μm as the ceramic raw material powder.

[0009]

However, in the conventional method for producing a ceramic slurry, it is difficult to sufficiently disperse a ceramic fine powder of 1 μm or less, and it is not possible to obtain a uniformly dispersed ceramic slurry. The fact is that it is difficult to produce a ceramic green sheet having a small thickness and high quality.

In a conventional method for producing a ceramic slurry, a ball mill filled with a cobblestone or a bead mill filled with beads is used to improve the dispersibility by applying a forced collision or impact force to the ceramic powder. In some cases, a method of dispersing is used, but in this case, the crushing force due to collision or impact is too large, damage to the ceramic powder is increased, and the crystallinity of the ceramic powder is reduced, and the specific surface area is increased. In addition, there is a problem that a multilayer ceramic electronic component having desired electric characteristics cannot be obtained.

As a method of dispersing the slurry, there has been proposed a high-pressure dispersion method in which a slurry containing ceramic powder is pressurized to a high pressure and caused to flow, and the ceramic powder is dispersed by collision or impact force. However, since the crushing force due to collisions and impacts is large, damage to the ceramic powder is large, measures to decrease the crystallinity of the ceramic powder and increase the specific surface area are insufficient, and the laminate with the desired electrical characteristics There remains a problem that ceramic electronic components cannot be obtained.

Further, the ceramic green sheet produced by using the ceramic slurry produced by the above-mentioned conventional method has insufficient surface smoothness, high density cannot be obtained, and tensile strength is insufficient. There is a problem that the distribution of the resin such as the binder and the plasticizer becomes non-uniform, and the shrinkage ratio in the firing step after lamination varies depending on the portion, and sufficient dimensional accuracy cannot be obtained.

The present invention has been made in view of such a background, and can uniformly disperse a ceramic powder without excessively damaging the ceramic powder, and is used for manufacturing a ceramic electronic component. It is an object of the present invention to provide a method for producing a ceramic slurry, a method for producing a ceramic green sheet, and a method for producing a multilayer ceramic electronic component, which can efficiently produce a ceramic slurry suitable for the above.

[0014]

In order to achieve the above object, a method for producing a ceramic slurry according to the present invention (claim 1) comprises mixing a ceramic powder having an average particle size of 0.01 to 1 μm with a dispersion medium. Press the mixed slurry to high pressure,
The ceramic powder in the mixed slurry is dispersed by passing the ceramic powder through a predetermined flow path at a flow rate capable of giving a maximum shear stress of 1000 [Pa] or more to the ceramic powder.

A mixed slurry of a ceramic powder having an average particle diameter of 0.01 to 1 μm and a dispersion medium is pressurized to a high pressure so that a maximum shear stress of 1000 [Pa] or more can be applied to the ceramic powder. As the mixed slurry passes through the predetermined flow path, the shear force required for dispersion is given to the ceramic powder without causing significant damage to the ceramic powder when the mixed slurry passes through the predetermined flow path. It becomes possible to disperse well. In the present invention, “a mixed slurry of ceramic powder and a dispersion medium” does not exclude a state including a binder, a dispersant, a plasticizer, an antistatic agent, and the like. That is,
The present invention has a sufficient effect even when a mixed slurry containing additives such as a binder, a dispersant, a plasticizer, and an antistatic agent is dispersed, and the mixed slurry containing the additive is dispersed. This case is also included in one embodiment of the method for producing a ceramic slurry of the present invention. Also,
The present invention is particularly advantageously applied when the average particle diameter of ceramic powder (average particle diameter determined by an electron microscope) is in the range of 0.01 to 1 μm. It is possible to apply even if it exceeds.

In the method for producing a ceramic slurry according to a second aspect, a mixed slurry obtained by mixing a ceramic powder having an average particle size of 0.01 to 1 μm and a dispersion medium is pressurized to a high pressure, and a predetermined flow path is formed. Wall shear rate of 10 when passing
^At a rate of ⁶ [1 / s] or more, the ceramic powder in the mixed slurry is dispersed.

By setting the wall shear rate of the mixed slurry to pass through the flow path at 10 ⁶ [1 / s] or more, the ceramic powder is not greatly damaged when the mixed slurry passes through the flow path. In addition, the ceramic powder can be reliably and efficiently dispersed. Note that there is a relationship between the maximum shear stress and the wall shear rate: maximum shear stress = wall shear rate × slurry viscosity.

In a third aspect of the present invention, the method is characterized in that the mixed slurry is pressurized to a pressure of 100 kg / cm ² or more and passes through the flow passage.

By pressing the mixed slurry to at least 100 kg / cm ² , more preferably at least 300 kg / cm ² ,
The wall shear rate in a predetermined channel is set to 10 ⁶ [1 / s]
Or a maximum shear stress of 1000
[Pa] or more, and the invention of the present application can be made effective.

According to a fourth aspect of the present invention, the ratio (length / representative diameter) _{RL / D} of the length of the flow path to the representative diameter is in the range of 30 ≦ _{RL / D} ≦ 1000. It is characterized by having. However, the representative diameter of the flow path, the cross-sectional shape in the direction orthogonal to the axial direction is (a) short side when rectangular, (b) diameter in the case of a circular tube, (c) in the case of an ellipse Minor diameter, (d) In other cases, the average fluid depth (=
4 x flow path cross-sectional area / total wetting length).

When the ratio (length / representative diameter) R _{L / D} of the length of the flow path to the representative diameter is set to 30 ≦ _{RL / D} ≦ 1000, the liquid passes through the flow path under practical conditions. The ceramic powder in the mixed slurry can be sufficiently dispersed, and the present invention can be made more effective.

The reason for setting R _{L / D} in the above range is as follows.
If _{RL / D} is less than 30, the ratio of the run-up section of the ceramic particles becomes large, and a sufficient crushing effect cannot be obtained. If it exceeds 1,000, the pressure loss is excessive for the crushing effect. It depends.

In the method for producing a ceramic slurry according to a fifth aspect, the flow path has a substantially straight portion having a predetermined length, and a bent portion having a bent angle of 100 ° or less is provided upstream and downstream thereof. It is characterized in that it is configured not to include a curved portion having a radius of curvature of 3 mm or less.

By providing a substantially linear portion of a predetermined length in the flow path, a maximum shear stress (1000 [Pa] or more) necessary for dispersing the ceramic powder is given, and the ceramic powder is reliably dispersed. Becomes possible,
On the upstream side and the downstream side of the substantially straight portion, the bending angle is 100 ° or less, and by not including the curved portion having a radius of curvature of 3 mm or less, before and after the slurry is supplied to the flow path, It is possible to prevent the ceramic powder from being greatly damaged by collision or impact force, and the present invention can be made more effective.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a ceramic green sheet, comprising forming the ceramic slurry produced by the first to fifth aspects on a predetermined base material into a sheet shape and forming a sheet having a thickness of 0.1 mm. It is characterized in that ceramic green sheets of 1 to 10 μm are formed.

The ceramic slurry produced by the method according to any one of claims 1 to 5 has an average particle size of 0.01 to 1 μm.
m of the ceramic powder is sufficiently dispersed in the dispersion medium, and is formed into a sheet to have a small thickness (0.
1 to 10 μm), making it possible to reliably produce high-quality ceramic green sheets. In other words, it has excellent surface smoothness, high density, high tensile strength, and
It is possible to obtain a ceramic green sheet suitable for use in manufacturing a multilayer ceramic electronic component, in which the distribution of a resin such as a binder and a plasticizer is uniform.

According to a seventh aspect of the present invention, there is provided a method for manufacturing a multilayer ceramic electronic component, wherein a ceramic green sheet is formed using the ceramic slurry manufactured by the first to fifth aspects, and the ceramic green sheet is formed together with a base metal internal electrode. After lamination, cutting, and firing, an external electrode is formed.

A ceramic green sheet is formed by using the ceramic slurry produced by the method according to any one of claims 1 to 5, and the ceramic green sheet is laminated with a base metal internal electrode, cut and fired, and then an external electrode is formed. Thus, it is possible to obtain a high-quality and highly reliable multilayer ceramic electronic component having desired characteristics.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be shown and the features thereof will be described in more detail.

In practicing the present invention, there are no particular restrictions on the type and specific composition of the ceramic powder, and dielectric ceramic powders such as barium titanate, strontium titanate and lead titanate, and ferrite powders The present invention can be widely applied to ceramic slurries using various ceramic powders such as magnetic ceramic powders, piezoelectric ceramic powders, and insulating ceramic powders such as alumina and silica.

Further, regarding the particle size of the ceramic powder,
Basically, it can be applied without any problem as long as it has a diameter passing through a high-pressure dispersing apparatus, but it is difficult to disperse by a conventional dispersing method. The average particle diameter obtained by an electron microscope is 0.01 to 1 μm.
When applied to ceramic powders, the effects of the present invention are most exhibited.

Further, the ceramic powder may contain an additive. For example, when the ceramic powder is mainly composed of barium titanate, glass as an additive,
It may contain magnesium oxide, manganese oxide, barium oxide, rare earth oxide, calcium oxide component and the like.

In the present invention, there is no particular limitation on the type of dispersion medium (solvent), and examples thereof include aromatic solvents such as toluene and xylene, and alcohol solvents such as ethyl alcohol, isopropyl alcohol and butyl alcohol. A dispersion medium (solvent) can be used, and one of these may be used alone or as a mixture. Further, as the dispersion medium, another organic solvent can be used, and water can be used.

As described above, the present invention can be applied to a case where a mixed slurry containing additives such as a binder, a dispersant, a plasticizer, and an antistatic agent is dispersed. As the binder that can be used when applying the present invention, a polyvinyl butyral resin, a cellulose resin, an acrylic resin, a vinyl acetate resin, and the like can be given. In addition, the kind and the amount of addition, etc., according to the target ceramic green sheet,
The type and amount are appropriately selected.

As a dispersant that can be used in the present invention, a preferred example is an anionic dispersant such as a carboxylate, a sulfonate or a phosphate. Further, a more preferable example is a polycarboxylic acid type containing no metal ion. There is no particular limitation on the dispersant, and various other dispersants can be used.

As the plasticizer, various plasticizers such as polyethylene glycol and phthalic acid ester are appropriately used. Further, the amount is selected according to the target ceramic green sheet.

The above-mentioned conditions for the additives such as the ceramic powder, the dispersion medium, the dispersant, and the plasticizer apply to all the claims of the present application.

FIG. 1 is a diagram showing a schematic configuration of a high-pressure dispersion apparatus used for carrying out the method for producing a ceramic slurry of the present invention. The high-pressure dispersing apparatus includes a raw material input unit 31 for inputting raw materials, a pressurizing unit 32 for pressing the input raw materials, a dispersing unit (flow path) 33 for passing and dispersing the pressurized raw materials (mixed slurry), A discharge section 34 is provided for discharging the dispersed slurry dispersed by passing through the substantially linear dispersion section (flow path) 33.

The dispersion section (flow path) 33 of this high-pressure dispersion apparatus
Is a linear portion having a rectangular cross section in a direction perpendicular to the axial direction, as shown in FIG.
mm, width W is 0.5 mm, and length L is 5 mm.

The dispersing section (flow path) 33 is formed as shown in FIG.
As shown in (1), a diamond layer 36 is provided on the inner peripheral surface of a square tube (outer tube) 35 made of stainless steel in order to ensure abrasion resistance.

FIGS. 4 and 5 show other examples of the structure of the dispersion section (flow path). FIG. 4 is a perspective view and FIG. 5 is a sectional view. As shown in FIGS. 4 and 5, the dispersing portion (flow path) 33 has a circular cross section in a direction perpendicular to the axial direction, and has a tapered taper such that the inner diameter becomes smaller as it goes further. It has a given structure. Further, in this dispersion portion (flow channel) 33, in order to secure abrasion resistance, as shown in FIGS. 4 and 5, a pipe 37 made of a cemented carbide having a diamond layer 36 formed on the inner peripheral surface is used. Has a structure pressed into the inside of a cylinder (outer cylinder) 35 made of stainless steel. The diamond layer 36 is formed such that the thickness increases as it proceeds, and the inner diameter of the dispersion portion (flow channel) 33 decreases.

However, in the present invention, there is no particular restriction on the shape and configuration of the dispersion section (flow path) 33 of the high-pressure dispersion apparatus, and the cross-sectional shape is not limited to a rectangle or a circle as described above. , A triangle, an ellipse, or a combination thereof.

The length of the dispersion section (flow path) 33 is such that the ratio of the flow path length to the representative diameter (length / representative diameter) _{RL / D} is 3
It is preferable that the range satisfy the condition of 0 ≦ _{RL / D} ≦ 1000. This is because, as described above, when _{RL / D} is less than 30, the ratio of the approaching section of the ceramic powder becomes large, and a sufficient crushing effect cannot be obtained.
Is exceeded, the pressure loss is excessive for the crushing effect. The dispersion section (flow path) 33 of the high-pressure dispersion apparatus used in this embodiment has a substantially straight section with a rectangular or circular cross section as described above, It is configured not to include a bent portion having a bending angle of 100 ° or less and a curved portion having a curvature radius of 3 mm or less.
Therefore, before and after the slurry is supplied to the dispersion portion (flow path) 33, the ceramic powder is not greatly damaged by collision or impact force, and a high-quality dispersion slurry can be obtained.

The mixed slurry is dispersed in a dispersion section (flow path) 33.
Wall shear rate when passing through⁶[1 / s] or less
It is preferred to be above. If the cross section of the flow channel is rectangular,
The speed γ is represented by the following equation. γ = Q × 6 / h²  Here, Q is the flow rate per unit width, and h is the height of the flow path.
It is. If the cross section of the channel is circular,
The speed γ is represented by the following equation. γ = 4Q_V/ Πa³  However, Q_VIs the volume flow rate and a is the radius of the flow path.

As described above, the flow path of the present invention having the above-described requirements is used when the mixed slurry passes under predetermined conditions.
Maximum shear stress of 1000 [Pa] or more, and / or 1
0 6 ^[1 / s] to generate more wall shear rate, the shear stress, or / and wall shear rate contributes to dispersion and crushing of the ceramic powder.

The above-mentioned materials (ceramic powder, dispersion medium, binder, dispersant, plasticizer, antistatic agent, etc.) are blended at a predetermined ratio, and the mixture is put into a cup, a stirrer, etc., and preliminarily mixed. When the slurry is introduced from the introduction section 31 of the high-pressure dispersing apparatus (FIG. 1), it is at least 100 kg / cm ² or more, preferably 300 kg / cm ² , in the pressure section 32.
Pressurized above. Then, the pressurized mixed slurry is dispersed by receiving a large shear stress generated by flowing at high speed through the flow path which is the dispersion section (flow path) 33.
Then, the dispersed slurry (dispersed slurry) is discharged to the discharge unit 3
4

Example 1 First, 2 parts by weight of an anionic dispersant and 10 parts by weight of an acrylic resin binder were added to 100 parts by weight of a commercially available ceramic powder having a particle diameter of 0.2 μm (here, barium titanate-based ceramic powder). Parts and 100 parts by weight of toluene to prepare a mixed slurry. Next, using the high-pressure dispersing apparatus shown in FIG. 1, the flow rate was adjusted so that the wall shear rate became 10 ⁶ [1 / s], and the mixed slurry was treated 10 times to obtain a dispersed slurry.

The dispersibility of the dispersion slurry thus obtained was evaluated by a particle size distribution analyzer manufactured by Microtrac Co., Ltd., and as a result, the integrated 90% particle diameter (D90) of the particle size distribution was:
Before high-pressure dispersion, it was confirmed that the dispersion of 32 μm became 0.45 μm. After the dispersion slurry was dried at 500 ° C., the specific surface area was measured. As a result, the rate of increase with respect to the original specific surface area was very small at 5%.

Next, the dispersion slurry was formed into a sheet by a doctor blade method to produce a ceramic green sheet. Then, the surface roughness (Ra) of the produced ceramic green sheet was measured with an atomic force microscope, and further, as a density ratio of the ceramic green sheet,
The ratio between the measured density and the theoretical density (measured density / theoretical density) was determined. As a result, Ra was 60 nm and the density ratio was 1.00.

Next, using this ceramic green sheet, as shown in FIG. 6, the internal electrodes 2 are provided in the ceramic element 1 and both ends of the ceramic element 1 are alternately provided on different sides. A multilayer ceramic capacitor having a structure in which a pair of external electrodes 3a and 3b are provided so as to be electrically connected to the internal electrode 2 drawn out to the end face was manufactured.

The method for manufacturing the multilayer ceramic capacitor is as follows. First, a Ni paste is screen-printed on the ceramic green sheet produced as described above to form an electrode-arranged sheet on which internal electrodes for capacitance formation are arranged. Next, as shown in FIG. 7, a predetermined number (here, 70 layers) of electrode arrangement sheets 11 are laminated, and ceramic green sheets (outer layer sheets) 21 on which electrodes are not arranged are formed on the upper and lower surfaces. By laminating and crimping, a laminated body (laminated crimped body) is formed in which one end side of each internal electrode 2 is alternately drawn to an end surface on a different side. Then, after the laminated pressure-bonded body is cut into a predetermined size by a dicer, binder removal and firing are performed. The binder is removed by heat treatment in a nitrogen atmosphere. The firing is performed by heating to a predetermined temperature in a weak reducing atmosphere. Then, a conductive paste containing silver as a conductive component is applied to both ends of the fired laminate (ceramic element) 1 and baked, so that the external electrodes 3 electrically connected to the internal electrodes 2 are formed.
a, 3b (FIG. 6) are formed. Thus, a multilayer ceramic capacitor using Ni as the internal electrode 2 as shown in FIG. 6 is obtained.

As a result of measuring the short-circuit rate (short-circuit occurrence rate) of the multilayer ceramic capacitor manufactured as described above, the short-circuit rate was as low as 3.0%, and good results were obtained. The temperature characteristics of the capacitance satisfied X7R.

Example 2 First, 2 parts by weight of an anionic dispersant, 100 parts by weight of toluene and 100 parts by weight of a commercially available ceramic powder having a particle diameter of 0.2 μm (here, a barium titanate-based ceramic powder) were used.
Mix parts by weight to obtain a mixed slurry. Next, using the high-pressure dispersing apparatus shown in FIG. 1, the flow rate was adjusted so that the wall shear stress became 1000 [Pa], and the mixed slurry was treated ten times to obtain a dispersed slurry.

The dispersibility of the thus-obtained dispersion slurry was evaluated using a particle size distribution analyzer manufactured by Microtrac, Inc. As a result, the integrated 90% particle diameter (D90) of the particle size distribution was:
Before high-pressure dispersion, it was confirmed that the dispersion of 32 μm became 0.47 μm. After the dispersion slurry was dried at 500 ° C., the specific surface area was measured. As a result, the rate of increase with respect to the original specific surface area was 4.5%, which was very small.

Next, this dispersed slurry was formed into a sheet by a doctor blade method to produce a ceramic green sheet. Then, the surface roughness (Ra) of the produced ceramic green sheet was measured with an atomic force microscope, and further, as a density ratio of the ceramic green sheet,
The ratio between the measured density and the theoretical density (measured density / theoretical density) was determined. As a result, Ra was 63 nm and the density ratio was 1.00.

Next, a multilayer ceramic capacitor was manufactured using the ceramic green sheets. The manufacturing method of the multilayer ceramic capacitor is the same as that of the first embodiment, and therefore the description is omitted to avoid duplication. As a result of measuring the short-circuit rate of the manufactured multilayer ceramic capacitor, the short-circuit rate was as low as 3.3%, and good results were obtained. The temperature characteristic of the capacitance is X7
R was satisfied.

Comparative Example 1 First, 2 parts by weight of an anionic dispersant and 10 parts by weight of an acrylic resin-based binder were added to 100 parts by weight of a commercially available ceramic powder having a particle diameter of 0.2 μm (here, a barium titanate-based ceramic powder). Parts and 100 parts by weight of toluene to prepare a mixed slurry. Next, this mixed slurry is mixed with a sand mill (cobblestone PSZ).
(Diameter 1mm) Addition amount 1000g, rotation speed 1000rpm
m, dispersion time 2 hours).

The dispersibility of the dispersion slurry thus obtained was evaluated by a particle size distribution analyzer manufactured by Microtrac Co., Ltd., and as a result, the integrated 90% particle size (D90) of the particle size distribution was 0.60 μm. In addition, this dispersed slurry is
After drying at 0 ° C., the specific surface area was measured. As a result, the rate of increase with respect to the original specific surface area was 30%. This is presumably because the ceramic powder was pulverized by collision with a cobblestone.

Next, the dispersion slurry was formed into a sheet by a doctor blade method to produce a ceramic green sheet. Then, the surface roughness (Ra) of the produced ceramic green sheet was measured with an atomic force microscope, and further, as a density ratio of the ceramic green sheet,
The ratio between the measured density and the theoretical density (measured density / theoretical density) was determined. As a result, Ra was 110 nm and the density ratio was 0.80.

Next, using the ceramic green sheets, a multilayer ceramic capacitor was manufactured in the same manner as in the first embodiment. As a result of measuring the short-circuit rate of the manufactured multilayer ceramic capacitor, it was as large as 50%, and the temperature characteristics of the capacitance did not satisfy X7R.

Comparative Example 2 First, 2 parts by weight of an anionic dispersant and 100 parts by weight of toluene were added to 100 parts by weight of a commercially available ceramic powder having a particle diameter of 0.2 μm (here, a barium titanate-based ceramic powder).
Mix parts by weight to obtain a mixed slurry. Next, this mixed slurry is mixed with a sand mill (cobblestone PSZ).
(Diameter 1mm) Addition amount 1000g, rotation speed 1000rpm
m, dispersion time 2 hours).

The dispersibility of the dispersion slurry thus obtained was evaluated by a particle size distribution analyzer manufactured by Microtrac Co., Ltd., and as a result, the integrated 90% particle size (D90) of the particle size distribution was 0.57 μm. In addition, this slurry is
After drying, the specific surface area was measured. As a result, the rate of increase relative to the original specific surface area was 28%.

Next, the dispersion slurry was formed into a sheet by a doctor blade method to produce a ceramic green sheet. Then, the surface roughness (Ra) of the produced ceramic green sheet was measured with an atomic force microscope, and further, as a density ratio of the ceramic green sheet,
The ratio between the measured density and the theoretical density (measured density / theoretical density) was determined. As a result, Ra was 110 nm and the density ratio was 0.80.

Next, using this ceramic green sheet, a multilayer ceramic capacitor was manufactured in the same manner as in the first embodiment. As a result of measuring the short circuit rate of the manufactured multilayer ceramic capacitor, the short circuit rate was 4
It was as high as 5%. The temperature characteristic of the capacitance is X7R
Was satisfied.

The present invention is not limited to the above-described embodiments and examples, but includes a type of a ceramic powder, a dispersion medium, or an additive, and a high-pressure dispersion apparatus used for high-pressure dispersion. Various applications and modifications can be made within the scope of the invention with respect to the general configuration and the like.

[0066]

As described above, the method for producing a ceramic slurry according to the present invention (claim 1) has an average particle size of 0.01.
A mixed slurry of a ceramic powder and a dispersion medium of about 1 μm is pressurized to a high pressure so that the ceramic powder is allowed to pass through a predetermined flow path under a condition capable of giving a maximum shear stress of 1000 [Pa] or more. Therefore, when the mixed slurry passes through the predetermined flow path, it is possible to efficiently disperse the ceramic powder by applying a shearing force necessary for dispersion without significantly damaging the ceramic powder.

Further, as in the method for producing a ceramic slurry according to the second aspect, by setting the wall shear rate when the mixed slurry passes through the flow path to 10 ⁶ [1 / s] or more, the mixed slurry can be formed in the flow path. When passing through, the ceramic powder can be surely and efficiently dispersed without seriously damaging the ceramic powder.

Further, as in the method for producing a ceramic slurry according to claim 3, the mixed slurry is not less than 100 kg / cm ² ,
By pressurizing to preferably 300 kg / cm ² or more,
The wall shear rate in a predetermined channel is set to 10 ⁶ [1 / s]
Or / and a maximum shear stress of 1000
[Pa] or more, and the present invention can be made effective.

Further, as in the method for producing a ceramic slurry according to claim 4, the ratio (length / representative diameter) _{RL / D} of the length of the flow path to the representative diameter is set to satisfy 30 ≦ _{RL / D} ≦ 1000. By doing so, it becomes possible to sufficiently disperse the ceramic powder in the mixed slurry passing through the flow path under practical conditions, and the present invention can be made more effective.

Further, as in the method for producing a ceramic slurry according to claim 5, the flow path has a substantially straight portion having a predetermined length, and a bend angle of 100 degrees is provided on the upstream and downstream sides.
場合 When the bent portion and the curved portion with a radius of curvature of 3 mm or less are not included, the maximum shear stress (1000 [Pa] or more) necessary for dispersing the ceramic powder is given to ensure that the ceramic powder is removed. In addition to being able to disperse, before and after the slurry is supplied to the flow path, it is possible to prevent the ceramic powder from being greatly damaged by collision or impact force, thereby making the present invention more effective. Will be able to do it.

Further, as in the method for producing a ceramic green sheet according to claim 6, ceramic powder having an average particle diameter of 0.01 to 1 μm, which is produced by the method of claims 1 to 5, is sufficiently dispersed in the dispersion medium. When ceramic green sheets are manufactured using the ceramic slurry, the thickness is as thin as 0.1 to 10 μm, and it is possible to reliably manufacture high quality ceramic green sheets.

Further, a ceramic green sheet is formed by using the ceramic slurry manufactured by the method of the present invention, and the ceramic green sheet is stacked together with the base metal internal electrode. After cutting, firing and forming the external electrodes, it is possible to obtain a high quality and highly reliable multilayer ceramic electronic component having desired characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a high-pressure dispersion apparatus used for carrying out a method for producing a ceramic slurry of the present invention.

FIG. 2 is a perspective view showing a dispersion section (flow path) of a high-pressure dispersion apparatus used for carrying out the method for producing a ceramic slurry of the present invention.

FIG. 3 is a sectional view of a dispersion section (flow path) of the high-pressure dispersion apparatus of FIG.

FIG. 4 is a perspective view showing another example of a dispersion section (flow path) of a high-pressure dispersion apparatus used for carrying out the method for producing a ceramic slurry of the present invention.

5 is a sectional view of a dispersion section (flow path) of the high-pressure dispersion apparatus of FIG.

FIG. 6 is a sectional view showing a laminated ceramic capacitor manufactured by laminating ceramic green sheets.

FIG. 7 is a diagram illustrating a method for manufacturing a multilayer ceramic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic element 2 Internal electrode 3a, 3b External electrode 11 Electrode arrangement sheet 21 Sheet for outer layer 31 Material input part 32 Pressurization part 33 Dispersion part (flow path) 34 Discharge part 35 Outer cylinder 36 Sintered diamond layer 37 Cemented carbide Tube consisting of

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G052 DA08 DB02 DC06 4G056 AA02 AA03 BA02 BA20 DA05 5E001 AB03 AC09 AE01 AE02 AE03 AE04 AF06 AH05 AH06 AH08 AH09 AJ02 5E082 AA01 AB03 BC38 BC40 EE04 FG23 FG23 FG11 GG28 HH43 JJ03 JJ12 JJ23 LL01 LL02 LL03 MM22 MM24 PP07 PP09 PP10

Claims (7)

[Claims] 1. A mixed slurry obtained by mixing a ceramic powder having an average particle diameter of 0.01 to 1 μm and a dispersion medium is pressurized to a high pressure, and a predetermined flow path is formed in the ceramic powder by 1000 [Pa].
A method for producing a ceramic slurry, comprising dispersing ceramic powder in the mixed slurry by passing the mixed slurry at a flow rate capable of giving the maximum shear stress. 2. A mixed slurry obtained by mixing a ceramic powder having an average particle size of 0.01 to 1 .mu.m and a dispersion medium is pressurized to a high pressure so that a wall shear rate when passing through a predetermined flow path is 10 to 10.
^{6. A} method for producing a ceramic slurry, comprising dispersing ceramic powder in the mixed slurry at a rate of 1 / s or more. 3. The method for producing a ceramic slurry according to claim 1, wherein said mixed slurry is pressurized to a pressure of 100 kg / cm ² or more and passed through said flow path. 4. The method according to claim 1, wherein a ratio (length / representative diameter) _{RL / D} of the length of the flow path to the representative diameter is in a range of 30 ≦ _{RL / D} ≦ 1000. 3. The method for producing a ceramic slurry according to any one of 3., wherein the representative diameter of the flow path is such that the cross-sectional shape in a direction perpendicular to the axial direction is
(a) short side in the case of a rectangle, (b) diameter in the case of a circular tube,
(c) In the case of an ellipse, the minor axis is shown, and in the other cases, the average fluid depth (= 4 × cross-sectional area of the channel / total wetting length) is shown. 5. The flow path has a substantially straight portion having a predetermined length, and a bending angle of 100 degrees is provided on the upstream and downstream sides thereof.
5. The apparatus according to claim 1, wherein the bent portion having a radius of curvature of 3 mm or less and a curved portion having a radius of curvature of 3 mm or less are not included.
The method for producing a ceramic slurry according to any one of the above. 6. A method of forming a ceramic green sheet having a thickness of 0.1 to 10 μm by forming the ceramic slurry produced by the method of claim 1 into a sheet on a predetermined substrate. Characteristic method of manufacturing ceramic green sheets. 7. A ceramic green sheet is formed by using the ceramic slurry produced by the method of claim 1, and the ceramic green sheet is laminated with a base metal internal electrode, cut and fired, and then an external electrode is formed. A method for manufacturing a multilayer ceramic electronic component, comprising: