JP2003192449A - Water-based coating composition for ceramic green sheet, method for manufacturing ceramic green sheet and method for manufacturing ceramic electronic parts - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based coating composition for a ceramic green sheet which can stably form a thick sheet without causing various defects such as cracks and orange peels even when a water-based solvent is used, and to provide a method for manufacturing a ceramic green sheet and a method for manufacturing ceramic electronic parts. <P>SOLUTION: The water-based coating composition for the ceramic green sheet comprises a ceramic source material, a binder resin and solvent water. The binder resin contains water-soluble polyvinylacetal resin and the polymerization degree of the water-soluble polyvinylacetal resin is ≤1,000, preferably 300 to 800. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic coating material capable of thickening a sheet without causing various defects such as cracks and citron skin even when an aqueous solvent is used, a method for producing a ceramic green sheet, and a ceramic. The present invention relates to a method of manufacturing an electronic component.

[0002]

2. Description of the Related Art In order to manufacture a ceramic electronic component such as a CR built-in type board and a laminated ceramic capacitor,
First, a ceramic coating composed of ceramic powder, binder (acrylic resin, butyral resin, etc.), plasticizer and organic solvent (toluene, MEK) is prepared. Next, this ceramic coating material is applied onto a PET film using a doctor blade method or the like, dried by heating, and then the PET film is peeled off to obtain a ceramic green sheet. Next, the internal electrodes are printed on this ceramic green sheet and dried, and the laminated ones are cut into chips to form green chips. After firing these green chips, the external electrodes are formed to form a laminated ceramic. Manufacture electronic components such as capacitors.

When manufacturing a monolithic ceramic capacitor, the interlayer thickness of the sheet on which the internal electrodes are formed is in the range of about 2 μm to 100 μm based on the desired capacitance required for the capacitor. Further, in the monolithic ceramic capacitor, a portion where the internal electrodes are not formed is formed on the outer side portion of the capacitor chip in the laminating direction.

The thickness of the dielectric layer corresponding to the portion where the internal electrode is not formed is about several hundreds of μm, and this portion is formed by using a relatively thick ceramic green sheet on which the internal electrode is not printed. . Since the thickness of the green sheet on which the internal electrodes are printed is relatively thin, if an attempt is made to mold the outer portion using this thin film green sheet, the number of laminated layers will increase, the number of manufacturing steps will increase, and the manufacturing cost will increase. Leads to an increase.

In the case of a ceramic paint containing an organic solvent, the molding thickness of the sheet can be relatively freely changed according to the purpose of the site of use, and a relatively thick film sheet can be molded.

On the other hand, in recent years, when manufacturing electronic parts,
It has been pointed out that not only the cost of the organic solvent but also the problem of the atmospheric release of the organic solvent due to drying and exhaust, that is, the problem of air pollution and global warming, and the cost of the solvent recovery device. Therefore, there is an increasing demand for a water-based binder that does not use an organic solvent as a binder for a ceramic green sheet coating material. Among water-based binders, polyvinyl alcohol is widely used because it has excellent coatability, high film strength, and excellent handleability as compared with other water-soluble binders.

[0007]

However, since polyvinyl alcohol is insoluble in solvents other than water,
Water is the only main solvent in the paint. Since water has a higher boiling point, a lower vapor pressure, and a higher specific heat than organic solvents, it is necessary to raise the drying temperature of the green sheet. As a result, cracks are likely to occur during the molding of the ceramic green sheet. Therefore, the molding thickness (for example, 100 μm to several hundreds of μm) of the relatively thick film green sheet, which is possible with the organic solvent-based paint, is
It was extremely difficult. That is, when a green sheet having a relatively thick film (for example, 100 μm to several hundreds μm) is formed by using a conventional water-based paint, defects such as cracks and citron skin occur.

Although a water-based green sheet paint using a water-soluble polyvinyl acetal resin as a binder has been proposed, a thick-film green sheet can be stably formed by selecting a water-soluble polyvinyl acetal resin having any structure. Whether it could be obtained was a future issue.

The present invention has been made in view of the above circumstances, and an aqueous ceramic green capable of stably thickening a sheet without causing various defects such as cracks and citron skin even when an aqueous solvent is used. An object of the present invention is to provide a coating composition for a sheet, a method for producing a ceramic green sheet, and a method for producing a ceramic electronic component.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have used a water-based solvent by using a water-soluble polyvinyl acetal resin having a specific polymerization degree or less as a water-soluble binder. In addition, they found that a thick film green sheet can be stably obtained without causing various defects such as cracks and citron skin, and completed the present invention.

That is, the water-based ceramic green sheet coating composition according to the present invention is a water-based ceramic green sheet coating composition containing at least a ceramic raw material, a binder resin, and solvent water, wherein the binder resin is: A water-soluble polyvinyl acetal resin is included, and the degree of polymerization of the water-soluble polyvinyl acetal resin is 1000 or less.

The method for producing a ceramic green sheet according to the present invention is a coating composition for an aqueous ceramic green sheet, which comprises at least a ceramic raw material, a binder resin, and solvent water, wherein the binder resin is
A step of preparing a coating composition for a water-based ceramic green sheet in which the water-soluble polyvinyl acetal resin has a degree of polymerization of 1000 or less, and a ceramic green using the coating composition for a water-based ceramic green sheet Forming the sheet.

In the method for producing a ceramic green sheet according to the present invention, preferably, the green sheet is continuously fed into a drying oven, and the green sheet is dried in the first half of the drying oven.
The method further comprises a step of drying at a temperature of 5 to 45 ° C., and the latter half of the drying furnace further comprises a step of gradually or stepwise raising the temperature to a temperature of 150 ° C. or less for drying. In the first half of the drying process, it was for the first time by the present inventors that the sheet can be thickened while preventing cracks and the like by drying at a temperature of 35 to 45 ° C. and then raising the temperature. Was found.

The method for producing a ceramic electronic component according to the present invention is a water-based ceramic green sheet coating composition containing at least a ceramic raw material, a binder resin, and solvent water, wherein the binder resin is a water-soluble polyvinyl acetal. A step of preparing a water-based ceramic green sheet coating composition containing a resin and having a degree of polymerization of the water-soluble polyvinyl acetal resin of 1000 or less, and forming a ceramic green sheet using the water-based ceramic green sheet coating composition. The method includes a step, a step of drying the green sheet, a step of stacking the dried green sheets to obtain a green chip, and a step of firing the green chip.

In the present invention, the water-soluble polyvinyl acetal resin preferably has a degree of polymerization of 300 to 800. If the degree of polymerization is too high, it becomes difficult to obtain the effects of the present invention. On the other hand, it is difficult to produce a resin having a too low degree of polymerization. Therefore, the above range is particularly preferable.

More preferably, the degree of acetalization of the water-soluble polyvinyl acetal resin is 25 mol% to 45%.
Mol%. In this case, preferably, the water-soluble polyvinyl acetal resin has a hydroxyl group content of 50 mol%.
It is larger, preferably 55 to 65 mol%. The present inventors have found for the first time that it is easy to increase the thickness of the green sheet by reducing the degree of acetalization. However, it is difficult to produce a resin having a too low degree of acetalization, and if it is too high, it tends to be insoluble in water. Therefore, the above range is preferable. Further, if the amount of hydroxyl groups is too small, the effect of the present invention is small, and if it is too large, the production thereof tends to be difficult.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the embodiments shown in the drawings. FIG. 1 is a schematic sectional view of a monolithic ceramic capacitor according to an embodiment of the present invention, and FIG.
1 is a cross-sectional view of the main part of the green sheet used in the manufacturing process of the capacitor shown in FIG. 3, FIG. 3 is a cross-sectional view of the main part of the green chip used in the manufacturing process of the capacitor shown in FIG. 1, and FIG. 4 is for manufacturing the green sheet shown in FIG. FIG. 5 is a schematic view showing the degree of polymerization and the degree of acetalization in the chemical formula of the binder resin contained in the coating composition of FIG. 5, FIG. 5 is a graph showing the drying method of the green sheet, FIG. 6 is the drying method shown in FIG. It is a graph which shows the relationship with thickness.

In this embodiment, a monolithic ceramic capacitor will be described as an example of a ceramic electronic component. As shown in FIG. 1, the monolithic ceramic capacitor 1 has a capacitor element body 10 having a structure in which interlayer dielectric layers 2 and internal electrode layers 3 are alternately laminated. A pair of external electrodes 4 is formed at both ends of the capacitor element body 10 so as to be electrically connected to the internal electrode layers 3 alternately arranged inside the element body 10. Capacitor element body 10
The shape is not particularly limited, but is usually a rectangular parallelepiped.
The size is not particularly limited, and may be an appropriate size depending on the application, but usually (0.6 to 5.6 mm)
It is about x (0.3 to 5.0 mm) x (0.3 to 1.9 mm).

The internal electrode layers 3 are laminated so that the end faces on the respective sides are alternately exposed on the surfaces of the two opposing end portions of the capacitor element body 10. The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and are connected to the exposed end faces of the alternately arranged internal electrode layers 3 to form a capacitor circuit.

In the capacitor element body 10, outer dielectric layers 20 are arranged at both outer ends of the internal electrode layer 3 and the interlayer dielectric layer 2 in the stacking direction to protect the inside of the element body 10. There is.

Dielectric Layers 2 and 20 The composition of the inter-layer dielectric layer 2 and the outer dielectric layer 20 is not particularly limited in the present invention, but is composed of, for example, the following dielectric ceramic composition. The dielectric ceramic composition of the present embodiment is a dielectric ceramic composition having a main component represented by BaTiO ₃ , for example. The auxiliary components contained in the dielectric porcelain composition together with the main component include Sr, Zr, Y, Gd, and T.
b, Dy, V, Mo, Zn, Cd, Ti, Sn, W, B
Illustrative are subcomponents containing at least one selected from oxides of a, Ca, Mn, Mg, Cr, Si, and P.

By adding the sub-components, it becomes possible to carry out low temperature firing without deteriorating the dielectric properties of the main components, and it is possible to reduce reliability failures when the interlayer dielectric layers are made thin, and to prolong the life. Can be realized. However, in the present invention, the composition of the interlayer dielectric layer is not limited to the above.

Although various conditions such as the number of laminated layers and the thickness of the interlayer dielectric layer 2 shown in FIG. 1 may be appropriately determined according to the purpose and application, in the present embodiment, the thickness of the interlayer dielectric layer 2 is 1
It is about 50 μm to 50 μm. The thickness of the outer dielectric layer 20 is, for example, about 100 μm to several hundreds μm.

Internal Electrode Layer 3 The conductive material contained in the internal electrode layer 3 is not particularly limited, but a base metal can be used because the constituent material of the interlayer dielectric layer 2 has reduction resistance. The base metal used as the conductive material is preferably Ni, Cu, a Ni alloy or a Cu alloy. When the main component of the internal electrode layer 3 is Ni, a method of firing in a low oxygen partial pressure (reducing atmosphere) is used so that the dielectric is not reduced. On the other hand, a method such as shifting the composition ratio of the dielectric material from the stoichiometric composition is used so that it is not reduced. The thickness of the internal electrode layer 3 may be appropriately determined according to the application, etc., but is usually 0.5.
It is about 5 μm.

External Electrode 4 The conductive material contained in the external electrode 4 is not particularly limited,
Usually, Cu, Cu alloy, Ni, Ni alloy or the like is used. Of course, Ag, Ag-Pd alloy, etc. can also be used. In the present embodiment, inexpensive Ni and Cu are used.
Alternatively, these alloys can be used. The thickness of the external electrode may be appropriately determined according to the application, etc., but is usually 1
It is preferably about 0 to 50 μm.

Manufacturing Method of Multilayer Ceramic Capacitor Next, a manufacturing method of the multilayer ceramic capacitor according to one embodiment of the present invention will be described. In this embodiment, a green chip is manufactured by a normal printing method or a sheet method using a paste, and after firing the green chip, the external electrodes are printed or transferred and fired. The manufacturing method will be specifically described below.

First, the dielectric layer paste is prepared. In this embodiment, the dielectric layer paste is composed of an aqueous ceramic green sheet coating composition containing at least a ceramic raw material (dielectric raw material), a binder resin, and solvent water. If necessary, a plasticizer, a dispersant, a wetting agent, etc. are added to this coating composition.

This dielectric layer paste can be used to form the inter-layer dielectric layer 2 and the outer dielectric layer 20 shown in FIG. 1, but the method of the present invention produces a thick film green sheet. Since it is assumed that the outer dielectric layer 20 having a large film thickness is formed, the following description will be made mainly.

In this embodiment, a water-soluble polyvinyl acetal resin is used as the binder resin, and the one having a polymerization degree of 1000 or less, preferably 300 to 800 is used. The chemical formula of the water-soluble polyvinyl acetal resin is shown in FIG. In the present embodiment, the degree of acetalization of the water-soluble polyvinyl acetal resin is preferably 25 mol% to
It is 45 mol% and the amount of hydroxyl groups is larger than 50 mol%. The mass ratio of the binder resin to 100 parts by mass of the dielectric material is preferably 1 to 8 parts by mass, more preferably 2 to 5 parts by mass.

The plasticizer is not particularly limited as long as it imparts flexibility to the binder resin, and examples thereof include amines, diols and triols. Examples of amines include triethanolamine (TEA), and examples of diols and triols include polyethylene glycol (PEG), glycerin, ethylene glycol, triethylene glycol, trimethylpropane, and the like. The weight ratio of the plasticizer to 100 parts by mass of the binder resin is preferably 50 to 150 parts by mass.

The dispersant is not particularly limited as long as it disperses powder particles so as not to condense, and examples thereof include polycarboxylic acid ammonium salt, allyl ether copolymer, benzenesulfonic acid sodium salt, graft compound dispersant, Examples include polyethylene glycol type nonionic dispersants. The weight ratio of the dispersant to 100 parts by mass of the dielectric material is preferably 0.1 to 2 parts by mass,
It is more preferably 0.2 or more and less than 1.5 parts by mass.

The wetting agent is not particularly limited as long as it improves the wettability between the powder particles and the dispersion medium, and examples thereof include polyethylene glycol type nonionic wetting agents and sulfonic acid type anionic wetting agents. . Dielectric material 1
The weight ratio of the wetting agent to 00 parts by mass is preferably 0.01 to 5 parts by mass.

The dielectric raw material includes a raw material forming a main component, a raw material forming a subcomponent, and a raw material forming a sintering aid, if necessary, depending on the composition of the dielectric ceramic composition described above. Is used. As the raw material for the main component, Ti,
An oxide of Ba, Sr, Ca, Zr and / or a compound which becomes an oxide by firing is used. As the raw material which constitutes the subcomponent, Sr, Y, Gd, Tb, Dy, V, M
o, Zn, Cd, Ti, Sn, W, Ba, Ca, Mn,
One or more selected from oxides of Mg, Cr, Si, and P and / or compounds that become oxides by firing,
Preferably, three or more kinds of single oxides or composite oxides are used.

In the manufacturing method according to the present invention, it is not always necessary to include the sintering aid in the dielectric material, but when the sintering aid is included, for example, Si or Li oxide and / or Alternatively, a compound that becomes an oxide by firing is used. Examples of the compound that becomes an oxide by firing include carbonate, nitrate, oxalate, and organometallic compound. Of course, an oxide and a compound that becomes an oxide by firing may be used together. As these raw material powders, those having an average particle diameter of about 0.005 to 5 μm are usually used. To obtain a dielectric material from such a material powder, for example, the following may be performed.

First, the starting materials are mixed in a predetermined amount ratio and wet-mixed by, for example, a ball mill. Then, it is dried by a spray dryer or the like and then calcined to obtain the dielectric oxide of the above formula which constitutes the main component. The calcination is usually 500 to 1300 ° C, preferably 500 to 10 ° C.
2 at 00 ° C, more preferably 800 to 1000 ° C
Perform in air for about 10 hours. Then, it is pulverized by a jet mill, a ball mill, or the like until it has a predetermined particle size, and a dielectric material is obtained. Subcomponents and sintering aids (SiO
₂ or Li ₂ O, etc.) is calcined separately from the main component and mixed with the obtained dielectric material.

The above-mentioned dielectric material, binder resin,
The plasticizer, the dispersant, the wetting agent, and the solvent water are mixed by, for example, a ball mill to form a paste (slurry). Upon mixing, the dielectric raw material, the dispersant, and the wetting agent are primarily mixed with a small amount of solvent water, and then the binder resin, the plasticizer, and the remaining solvent water are secondarily mixed, whereby You may obtain the dielectric layer paste which consists of a coating composition.

In the present embodiment, the doctor blade method is used as a means for forming the dielectric layer paste into a sheet. As a support film for forming this sheet, for example, a PET film without Si treatment is used. A dielectric layer paste is applied to the support film to a predetermined thickness by the doctor blade method and dried.

That is, the PET support film (non-magnetic support) 30 shown in FIG. 2 is used. A dielectric layer paste is applied to the support film 30 by a doctor blade method to a predetermined thickness and dried.

After that, the exterior green sheet 20a obtained by peeling off the support film 30 is a portion constituting the outer dielectric layer 20 shown in FIG. 1, and is usually 100 to 50.
It has a film thickness of about 0 μm. Aside from the exterior green sheet 20a, 1 μm to 50 μm is formed by the same method.
The interior green sheet 2a that is molded to a relatively thin thickness is formed. The internal electrode layer 3 shown in FIG. 1 is formed on one surface of the interior green sheet 2a. The method for forming the internal electrode layer 3 is not particularly limited, but a printing method, a thin film method, or the like is exemplified.

Thereafter, as shown in FIG. 3, the interior green sheets 2a on which the internal electrode layers are formed are alternately laminated, and the exterior green sheets 20a are formed as a single layer or a plurality of layers on both outer ends in the laminating direction. Laminate in layers.

Next, the laminate thus obtained is
After cutting into a predetermined stack size to obtain the green chip 100, binder removal processing and firing are performed. Then, heat treatment is performed to re-oxidize the dielectric layers 2 and 20.

The binder removal treatment may be carried out under normal conditions, but when a base metal such as Ni or Ni alloy is used as the conductor material of the internal electrode layers, it is particularly preferably carried out under the following conditions.

Temperature rising rate: 5 to 300 ° C./hour, especially 10
~ 50 ° C / hour, holding temperature: 200 to 300 ° C, holding time: 0.5 to 20 hours, particularly 1 to 10 hours, atmosphere: in air.

The following firing conditions are preferable. Temperature rising rate: 50 to 500 ° C./hour, especially 200 to 300
C./hour, holding temperature: 1000 to 1400 ° C., holding time: 0.5 to 8 hours, especially 1 to 3 hours, cooling rate: 50 to 500 ° C./hour, especially 200 to 300
° C / hour, atmosphere gas: a mixed gas of humidified N ₂ and H _2, and the like.

However, the oxygen partial pressure during firing is 10^-2P
a or less, especially 10^-2-10^-10 Can be done in Pa
preferable. If the content exceeds the above range, the internal electrode layers will be oxidized.
If the oxygen partial pressure is too low, the internal
The electrode material of the electrode layer causes abnormal sintering and breaks
There is a tendency.

In the heat treatment after such firing, the holding temperature or the maximum temperature is preferably 1000 ° C. or higher,
More preferably, it is carried out at 1000 to 1100 ° C. If the holding temperature or maximum temperature during heat treatment is less than the above range, the insulation resistance life tends to be shortened due to insufficient oxidation of the dielectric material, and if it exceeds the above range, Ni of the internal electrode is oxidized and the capacity is Not only does it decrease, but it also reacts with the dielectric body, and the life tends to be shortened. The oxygen partial pressure during the heat treatment is higher than that in the reducing atmosphere during firing, and preferably 10 ⁻³ Pa to 1 P.
a, more preferably 10 ⁻² Pa to 1 Pa. If it is less than the above range, it is difficult to reoxidize the dielectric layers 2 and 20, and if it exceeds the above range, the internal electrode layer 3 tends to be oxidized. And the other heat treatment conditions are preferably as follows.

Holding time: 0 to 6 hours, especially 2 to 5 hours, cooling rate: 50 to 500 ° C./hour, especially 100 to 300
° C / hour, atmosphere gas: humidified N ₂ gas or the like.

To wet the N ₂ gas, mixed gas, etc., for example, a wetter or the like may be used. In this case, the water temperature is preferably 0 to 75 ° C. The binder removal treatment, firing and heat treatment may be performed continuously or independently. When performing these continuously, the atmosphere was changed without cooling after the binder removal treatment, the temperature was raised to the holding temperature during firing, firing was performed, and then cooling was performed to reach the holding temperature for heat treatment. It is sometimes preferable to change the atmosphere and perform the heat treatment. On the other hand, when performing these independently, at the time of firing was N ₂ gas or wet to the holding temperature of the binder removal process N ₂
After the temperature is raised in a gas atmosphere, it is preferable to change the atmosphere and continue to raise the temperature. After cooling to the holding temperature during the heat treatment, the atmosphere is changed again to N ₂ gas or a humidified N ₂ gas atmosphere and then cooled. It is preferable to continue. Further, in the thermal treatment, after raising the temperature to the holding temperature under N ₂ gas atmosphere, then change the atmosphere or a wet N ₂ gas atmosphere the entire process of the heat treatment.

The thus obtained sintered body (element body 10) is subjected to end face polishing by, for example, barrel polishing, sand plast, etc., and the external electrode paste is baked to form the external electrodes 4. The external electrode paste is generally prepared by kneading a conductive material made of various conductive metals or alloys, or various oxides, organometallic compounds, resinates, etc., which become the conductive material after firing, and an organic vehicle. To do. The monolithic ceramic capacitor of the present invention thus manufactured is mounted on a printed circuit board or the like by soldering or the like, and is used in various electronic devices or the like.

According to the method for manufacturing a monolithic ceramic capacitor according to the present embodiment, even if an aqueous solvent is used, various defects such as cracks and citron skin do not occur, and a thick film can be stably formed. It is also possible to form the relatively thick outer dielectric layer 20 as a single layer. As a result, the manufacturing cost of the capacitor can be reduced.

The present invention is not limited to the above-mentioned embodiment, but can be variously modified within the scope of the present invention.

[0052]

EXAMPLES The present invention will be described below based on more detailed examples, but the present invention is not limited to these examples.

Example 1 First, as a starting material main component (base material), BaTiO _{3 was used.}
(BT-05 powder / manufactured by Sakai Chemical Industry Co., Ltd.) was used. Its average particle diameter was 0.86 μm, and its specific surface area was 2.3 m ² / g in terms of BET value. With respect to 100 parts by mass of the main component, (Ba, Ca) SiO 2 is added as an accessory component.
₃ : 1.48 parts by mass, Y ₂ O ₃ : 1.01 parts by mass,
MgCO _3: 0.72 parts by _weight, Cr ₂ O 3: 0.
13 parts by weight and _V 2 _O 5: were prepared 0.045 parts by mass. First, only the subcomponent additives were mixed in a ball mill to form a slurry.

The auxiliary component additive (total amount: 3.385 g) and ion-exchanged water 7.723 g were preliminarily ground for 20 hours by a ball mill. Then, BaTiO _3: against 100 g, and the pre-ground slurry 11.108g subcomponent additives, ion exchange water: 92.25
4g, dispersing agent (graft compound of allyl alcohol, maleic anhydride and styrene copolymer and polyoxyalkylene monoalkyl ether: NOF Marialim AKM)
0531: 0.4 part by mass, wetting agent (acetylene diol-based surfactant: air products, Surfynol-465
0.4 part by mass) and add 16 parts by ball mill.
Mixed for hours. Next, a polyvinyl acetal resin (degree of polymerization: 400, degree of acetalization: 30 mol%, residual acetyl group: 12 mol) as a binder was added to the dispersion paint.
%, Hydroxyl group: 58 mol%, solid content concentration 30% lacquer) was added as a solid content in an amount of 2.5 parts by mass. Also, as a plasticizer,
100 parts by mass of polyethylene glycol 400 was added to 100 parts by mass of the binder. The coating material to which the binder and the plasticizer were added was further mixed in a ball mill for 16 hours to obtain a ceramic coating material (water-based ceramic green sheet coating composition).

The obtained coating material was applied to a PET film as a supporting film in various thicknesses by the doctor blading method. The drying condition is that the temperature in the drying oven is 25 ℃ to 70 ℃.
The drying temperature gradient was 0.714 ° C./minute, and the drying time was 63 minutes. Then, the limit film formation thickness of the green sheet was evaluated.

The limit film thickness was determined as follows. The coating thickness on the support film was increased by about 10 to 20 μm, for example, based on 200 μm, and the film formation state after the sheet was dried was evaluated. After the film is formed, the green sheet may have cracks at both ends, the center, and the entire surface, or the surface may be in a yuzu-skin state. The maximum sheet forming thickness at which such a problem does not occur was defined as the limit film forming thickness. The crack and the citron skin were evaluated visually. When the limit film formation thickness was 300 μm or more, it was evaluated as ◯, when 400 μm or more was evaluated as ⊚, and when it was less than 300 μm, it was evaluated as x. The results are shown in Table 1.

[0057]

[Table 1]

Example 2 As a binder in a ceramic coating, the degree of polymerization was 60.
Green sheets were formed into a film in the same manner as in Example 1 except that the polyvinyl acetal resin of No. 0 was used, and the limit film formation thickness of these green sheets was evaluated. The results are shown in Table 1.

Example 3 As a binder in a ceramic coating, the degree of polymerization was 80.
Green sheets were formed into a film in the same manner as in Example 1 except that the polyvinyl acetal resin of No. 0 was used, and the limit film formation thickness of these green sheets was evaluated. The results are shown in Table 1.

Comparative Example 1 As a binder in a ceramic coating, the degree of polymerization was 15
A green sheet was formed into a film in the same manner as in Example 1 except that the polyvinyl acetal resin of No. 00 was used, and the limit film formation thickness of these green sheets was evaluated. The results are shown in Table 1.

Example 4 As a binder in a ceramic coating, the degree of polymerization was 60.
0, the degree of acetalization is 45 mol% and the amount of hydroxyl groups is 53
Green sheets were formed into a film in the same manner as in Example 1 except that the polyvinyl acetal resin was used in an amount of mol%, and the limiting film formation thickness of these green sheets was evaluated. The results are shown in Table 1.

Reference Example 1 As a binder in a ceramic coating, the polymerization degree was 60.
0, the degree of acetalization is 38 mol%, and the amount of hydroxyl groups is 50.
Green sheets were formed into a film in the same manner as in Example 1 except that the polyvinyl acetal resin was used in an amount of mol%, and the limiting film formation thickness of these green sheets was evaluated. The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that polyvinyl alcohol (PVA205, saponification degree 88%, polymerization degree 500) was used as the water-soluble binder in the ceramic coating.
A green sheet was formed into a film, and the limit film forming thickness of these green sheets was evaluated. The results are shown in Table 1.

Evaluation As shown in Table 1, by comparing Example 2 and Comparative Example 2 having substantially the same degree of polymerization, it was confirmed that a water-soluble polyvinyl acetal resin is preferable as the binder. When PVA is used as the binder, the strength of the sheet is insufficient, and the water-soluble polyvinyl acetal resin is preferable also from this point. In addition, Examples 1 to 4 and Comparative Example 1
By comparing with, the polymerization degree of the binder resin is 100
It was confirmed that 0 or less, particularly 800 or less, is preferable in terms of thickening the film. It is difficult to synthesize a resin having a degree of polymerization smaller than 300.

Further, by comparing Example 4 with Reference Example 1, it was found that the amount of hydroxyl groups was larger than 50 mol%.
It was confirmed that it is preferable in terms of thickening the film. However, if the amount of hydroxyl groups is too large, its production tends to be difficult.

Furthermore, by comparing Examples 1 to 4, it was confirmed that the degree of acetalization of the binder resin is preferably 25 mol% to 45 mol% in terms of thickening the film. It should be noted that it is difficult to produce a resin having a too low degree of acetalization, and if it is too high, it tends to be insoluble in water.

Example 5 As shown in FIG. 5, Example 3 was repeated except that the drying temperature profile of the green sheet was changed to settings 1-5.
In the same manner as above, a green sheet was formed into a film, and the limiting film forming thickness of these green sheets was evaluated. Results are shown in FIG. As shown in FIG. 6, in the first half inside the drying furnace,
Dried at a temperature of ~ 45 ° C, especially 40 ° C ± 3 ° C,
In the latter half of the drying furnace, the temperature is gradually or stepwise raised to a temperature of 150 ° C. or lower, preferably 130 ° C. or lower, more preferably 75 ° C. or lower, particularly 70 ° C., and dried. It was confirmed that this is preferable in terms of thickening the film.

[0068]

As described above, according to the present invention, even if an aqueous solvent is used, it is possible to stably form a thick film of a sheet without causing various defects such as cracks and citron skin. A coating composition for a ceramic green sheet, a method for producing a ceramic green sheet, and a method for producing a ceramic electronic component can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a monolithic ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a green sheet used in a manufacturing process of the capacitor shown in FIG.

3 is a cross-sectional view of a main part of a green chip used in a manufacturing process of the capacitor shown in FIG.

FIG. 4 is a schematic diagram showing the degree of polymerization and the degree of acetalization in the chemical formula of the binder resin contained in the coating composition for producing the green sheet shown in FIG.

FIG. 5 is a graph showing a method for drying a green sheet.

FIG. 6 is a graph showing the relationship between the drying method shown in FIG. 5 and the film thickness of the green sheet.

[Explanation of symbols]

1. Multilayer ceramic capacitor 2 ... Interlayer dielectric layer 2a ... Green sheet for interior 20 ... Outer dielectric layer 20a ... Green sheet for exterior 3 ... Internal electrode layer 4 ... External electrode 10 ... Capacitor element body 30 ... PET support film 100 ... Green Chip

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomoko Uchida             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 4G030 AA02 AA07 AA08 AA09 AA10                       AA12 AA16 AA17 AA19 AA22                       AA37 BA09 CA08 GA04 GA05                       GA08 GA14 GA15 GA16 GA17                       GA20 GA24 GA27 PA22 PA25                 4J100 AF15 BA02 CA01 DA02 DA33                       DA38 JA01                 5E001 AB03 AE00 AH05 AH09 AJ02

Claims (13)

[Claims] 1. A water-based ceramic green sheet coating composition comprising at least a ceramic raw material, a binder resin, and solvent water, wherein the binder resin contains a water-soluble polyvinyl acetal resin, and the water-soluble polyvinyl acetal resin. Is a coating composition for water-based ceramic green sheets, characterized by having a degree of polymerization of 1000 or less. 2. The coating composition for a water-based ceramic green sheet according to claim 1, wherein the water-soluble polyvinyl acetal resin has a degree of polymerization of 300 to 800. 3. The coating composition for a water-based ceramic green sheet according to claim 1, wherein the degree of acetalization of the water-soluble polyvinyl acetal resin is 25 mol% to 45 mol%. 4. The coating composition for an aqueous ceramic green sheet according to claim 3, wherein the water-soluble polyvinyl acetal resin has a hydroxyl group content of more than 50 mol%. 5. A water-based ceramic green sheet coating composition comprising at least a ceramic raw material, a binder resin, and solvent water, wherein the binder resin contains a water-soluble polyvinyl acetal resin. Of a water-based ceramic green sheet coating composition having a degree of polymerization of 1000 or less, and a step of forming a ceramic green sheet using the water-based ceramic green sheet coating composition. Method. 6. The green sheet is continuously fed into a drying oven, and the front half of the drying oven has a temperature of 35 to 45 °.
The method for producing a green sheet according to claim 5, further comprising a step of drying at a temperature of C, and gradually or stepwise heating up to a temperature of 150 ° C. or less in the latter half of the drying oven to dry. . 7. The method for producing a green sheet according to claim 5, wherein the water-soluble polyvinyl acetal resin has a degree of polymerization of 300 to 800. 8. The method for producing a green sheet according to claim 5, wherein the degree of acetalization of the water-soluble polyvinyl acetal resin is 25 mol% to 45 mol%. 9. The method for producing a green sheet according to claim 8, wherein the amount of hydroxyl groups of the water-soluble polyvinyl acetal resin is larger than 50 mol%. 10. A ceramic raw material, a binder resin,
A coating composition for an aqueous ceramic green sheet having at least solvent water, wherein the binder resin contains a water-soluble polyvinyl acetal resin, and the degree of polymerization of the water-soluble polyvinyl acetal resin is 1000 or less. A step of adjusting the coating composition; a step of molding a ceramic green sheet using the coating composition for the water-based ceramic green sheet; a step of drying the green sheet; and a step of stacking the dried green sheets to form a green chip. And a step of firing the green chip, a method of manufacturing a ceramic electronic component. 11. The method for producing a ceramic electronic component according to claim 10, wherein the water-soluble polyvinyl acetal resin has a degree of polymerization of 300 to 800. 12. The method for producing a ceramic electronic component according to claim 10, wherein the degree of acetalization of the water-soluble polyvinyl acetal resin is 25 mol% to 45 mol%. 13. The method for producing a ceramic electronic component according to claim 12, wherein the water-soluble polyvinyl acetal resin has a hydroxyl group content of more than 50 mol%.