JP6897278B2 - Nickel paste and nickel paste manufacturing method - Google Patents

Description

The present invention relates to a nickel paste that can be suitably used for an internal electrode of a multilayer ceramic capacitor, and a method for producing the same.

Generally, the nickel paste used for the internal electrode of a multilayer ceramic capacitor (hereinafter, also referred to as "MLCC") is produced by kneading nickel powder in a vehicle and contains a large amount of agglomerates of nickel powder. The final step in the nickel powder manufacturing process usually includes a drying step regardless of the metal powder manufacturing method (dry method, wet method), and this drying step promotes the aggregation of nickel particles. Generally, the nickel powder produced contains agglomerates formed during drying.

In recent years, monolithic ceramic capacitors are required to increase the number of laminated ceramic green sheets with an internal electrode layer from several hundreds to about 1,000 layers in order to achieve a small size and a large capacity. For this reason, studies have been made to reduce the thickness of the internal electrode layer from the conventional several μm level to the submicron level, and along with this, the particle size of nickel powder, which is an electrode material for internal electrodes, has been reduced. Has been done.

However, the smaller the particle size of nickel powder, the larger the surface area, and the larger the surface energy, and the more easily agglomerates are formed. Metal ultrafine powder such as nickel ultrafine powder has poor dispersibility, and when aggregates are present, the aggregates penetrate the ceramic sheet layer when the nickel powder is sintered in the firing process during the production of ceramic capacitors. Therefore, the electrode is short-circuited and becomes a defective product. Further, even if the ceramic sheet layer cannot be penetrated, the short distance between the electrodes causes partial current concentration, which causes deterioration of the life of the multilayer ceramic capacitor.

Examples of the nickel ultrafine powder slurry used for the internal electrode of the MLCC include the slurry disclosed in Patent Document 1. Specifically, Patent Document 1 discloses the following techniques. That is, first, for a metal ultrafine powder water slurry (metal ultrafine powder concentration: 50% by mass) to which a specific anionic surfactant is added at a ratio of 0.3 parts by mass with respect to 100 parts by mass of the metal ultrafine powder. Then, a dispersion treatment using a process homogenizer or the like is carried out for a predetermined time to disperse the aggregates of the metal ultrafine powder in water to the primary particles. Then, as an organic solvent, for example, tarpineol is added in an amount of 10 parts by mass with respect to 100 parts by mass of the ultrafine metal powder. As a result, the tarpineol layer containing the metal powder becomes a continuous layer and becomes a precipitate, and water is separated as a supernatant to obtain a metal ultrafine powder organic solvent slurry.

Japanese Unexamined Patent Publication No. 2006-63441

However, in the production method described in Patent Document 1, in order to prepare a nickel powder organic slurry, a specific anionic surfactant is added directly to the nickel powder water slurry, and then the nickel powder is mixed with an organic solvent to prepare the nickel powder. Is replaced to obtain a nickel powder organic slurry. Therefore, the added surfactant is converted into micelles, which makes it difficult for the added surfactant to be adsorbed on the surface of the nickel powder, and it cannot be said that the aggregation of the nickel powder is efficiently suppressed. When the nickel powder aggregates and the dispersibility deteriorates, the surface roughness becomes large and the water cannot be removed efficiently.

Further, when producing the nickel powder organic slurry, some of the dispersants used to suppress the aggregation of the nickel powder have relatively high reactivity with the binder resin of the ceramic green sheet. When a nickel internal electrode ceramic capacitor is produced using a nickel powder organic slurry containing such a dispersant, the binder resin contained in the ceramic green sheet is dissolved to cause holes and wrinkles in the ceramic green sheet. So-called "seat attack" may occur. If this "sheet attack" is large, there will be problems such as holes in the printed portion of the nickel paste when the ceramic green sheets are laminated, and delamination between the ceramic green sheet and the internal electrode layer during firing. The thinner the ceramic green sheet, the more pronounced the effect of "sheet attack".

The present invention has been proposed in view of such circumstances, and an object of the present invention is to provide a nickel paste having excellent dispersibility of nickel powder and not causing sheet attack.

The present inventors have made extensive studies to solve the above-mentioned problems. As a result, according to the nickel paste containing a specific polymer dispersant, nickel powder has excellent dispersibility and can suppress the occurrence of sheet attack when used as an internal electrode of a multilayer ceramic capacitor. The present invention was completed with the knowledge that it becomes a paste. That is, the present invention provides the following.

(1) The first invention of the present invention is a nickel paste used for an internal electrode of a multilayer ceramic capacitor, which contains at least nickel powder, an organic solvent, a polymer dispersant, and a binder resin, and has the above-mentioned high content. The molecular dispersant is a nickel paste having a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane, and polyoxyalkylene as a lipophilic group.

(2) In the second invention of the present invention, in the first invention, the polymer dispersant is contained in a proportion of 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of nickel powder. It is a paste.

(3) The third invention of the present invention is the nickel paste in the first or second invention, wherein the average particle size of the nickel powder by the imaging method is 0.05 μm or more and 0.5 μm or less.

(4) The fourth invention of the present invention is a nickel organic slurry forming step of adding an organic solvent and a polymer dispersant to a nickel powder water slurry to form a nickel organic slurry, and an aqueous layer and an organic layer. There is a water separation step of separating the aqueous layer from the nickel organic slurry separated into the above to obtain an organic layer nickel organic slurry, and a kneading step of adding a binder resin to the organic layer nickel organic slurry and kneading. A method for producing a nickel paste, wherein the polymer dispersant has a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane, and polyoxyalkylene as a lipophilic group.

According to the present invention, it is possible to provide a nickel paste having excellent dispersibility of nickel powder and capable of suppressing the occurrence of sheet attack.

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be appropriately modified without changing the gist of the present invention. Further, in the present specification, the notation of "x to y" (x and y are arbitrary numerical values) means "x or more and y or less" unless otherwise specified.

≪1. Nickel paste ≫
The nickel paste according to the present embodiment is a nickel paste containing at least nickel powder, a polymer dispersant, an organic solvent, and a binder resin. The polymer dispersant has a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane, and polyoxyalkylene as a lipophilic group.

According to such a nickel paste, the dispersibility of nickel powder, which is a component, is excellent, and it is possible to prevent the occurrence of sheet attack when it is used as the internal electrode of a multilayer ceramic capacitor, and the internal electrode of the highly laminated ceramic capacitor can be prevented. It can be suitably used for use.

Such a nickel paste having excellent dispersibility of nickel powder has a viscosity of 8 Pa · s to 150 Pa · s, and a water content measured by the Karl Fischer method is less than 1% by mass. The surface roughness of the dry film obtained by applying the nickel paste is 0.05 μm or less.

[Nickel powder]
The nickel powder is a constituent component of the nickel paste, and various nickel powders can be used regardless of the production method such as a wet method or a dry method. For example, nickel powder may be obtained by a so-called dry method such as a CVD method, an evaporation quenching method, or a hydrogen reduction method using a nickel salt or nickel hydroxide, or a reducing agent such as hydrazine may be added to a nickel salt solution. Nickel powder by a so-called wet method such as the wet reduction method used may be used. Among them, it is preferable to use nickel powder by a so-called wet method such as a wet reduction method.

Further, the nickel powder is preferably ultrafine particles having an average particle size of 0.05 μm to 0.5 μm as measured by an imaging method. The ultrafine nickel powder can be suitably used, for example, as an internal electrode of a multilayer ceramic capacitor. From the viewpoint of responding to the thinning required in recent years as the internal electrode of MLCC, it is preferably necessary to use nickel powder having an average particle size of about 0.05 μm to 0.3 μm, and particularly inside the 1000 layer level. In order to use the electrode, nickel powder having an average particle size of submicron is required, and it is more preferable to use nickel powder having an average particle size of 0.05 μm to 0.1 μm.

The imaging method used for measuring the average particle size is that the nickel powder to be measured is observed using a scanning electron microscope (SEM), and 100 primary particles existing within a predetermined range of the SEM observation image. This is a method of measuring the diameter and using the average value as the average particle size. Here, the primary particles refer to unit particles observed by a scanning electron microscope (SEM), and do not mean particles formed by aggregating and combining unit particles, so-called secondary particles.

The nickel content in the nickel paste is not particularly limited, but is preferably 50% by mass to 70% by mass. If the nickel content is less than 50% by mass, it becomes difficult to obtain conductivity as an internal electrode of the monolithic ceramic capacitor. On the other hand, when the nickel content exceeds 70% by mass, it becomes easy to peel off from the ceramic sheet in the firing step.

[Polymer dispersant]
The polymer dispersant is adsorbed and coated on the surface of the nickel powder and acts to improve the dispersibility in the nickel paste. This polymer dispersant has a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane and polyoxyalkylene as a lipophilic group.

Here, the surface of the nickel powder has a basic property. Therefore, as the polymer dispersant, a polymer dispersant having the above structure (having a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane and polyoxyalkylene as a lipophilic group) By containing the above, the nickel powder can be efficiently adsorbed on the surface of the nickel powder, and the dispersibility can be improved. Further, since the polymer dispersant has the above structure, the reactivity of the ceramic green sheet with the binder resin is low, and the occurrence of sheet attack can be prevented.

The molecular weight of the polymer dispersant is not particularly limited, but is preferably 500 or more, and more preferably 1000 or more, for example. The molecular weight of the polymer dispersant is preferably 100,000 or less, and more preferably 80,000 or less. The "molecular weight" means a weight average molecular weight.

The structure of the polymer dispersant is not particularly limited, but a comb-shaped polymer is preferable. As the polymer dispersant having a comb-shaped structure, it is preferable that the anchor portion corresponding to the back of the comb has a phosphoric acid group and the graft portion corresponding to the teeth of the comb has polyester, polyamide, polyurethane, or polyoxyalkylene. By being a polymer dispersant having a comb-shaped polymer structure in this way, the phosphate group of the anchor portion is efficiently adsorbed on the nickel powder, and the graft portion that hits the teeth of the comb exerts a steric hindrance effect. It suppresses the aggregation of nickel powder more effectively.

Specifically, as such a polymer dispersant, a polymer dispersant having a phosphoric acid group as a hydrophilic group and a polyamide as a lipophilic group (trade name: SOLPERSE36000, manufactured by Nippon Lubrizol) and a hydrophilic group Examples of the polymer dispersant having a phosphoric acid group and a polyester as a lipophilic group (trade names: DISPER BYK-110, BYK-111, BYK-118, BYK-181, manufactured by Big Chemie Japan) and the like can be mentioned. , Can be preferably used.

The content of the polymer dispersant is not particularly limited, but is preferably 2 parts by mass to 10 parts by mass with respect to 100 parts by mass of the nickel powder, and is preferably 2 parts by mass to 8 parts by mass. Is more preferable, and the ratio is more preferably 2 parts by mass to 5 parts by mass. If the content of the polymer dispersant is less than 2 parts by mass with respect to 100 parts by mass of the nickel powder, water may not be separated efficiently during kneading to prepare the nickel paste, and the nickel paste contains The amount of residual water in the paste increases. On the other hand, if it exceeds 10 parts by mass with respect to 100 parts by mass of the nickel powder, water may be trapped in the polymer dispersant when coating the surface of the nickel powder, and the water content in the nickel paste may remain. , Too much polymer dispersant can affect the viscosity of the nickel paste.

[Organic solvent]
The organic solvent is usually a solvent generally used as a solvent for a conductive paste, and is not particularly limited as long as it is a solvent capable of dissolving the above-mentioned polymer dispersant. Among them, it is preferable to use an organic solvent such as a terpene alcohol type or an aliphatic hydrocarbon type.

Specifically, examples of the terpene alcohol-based organic solvent include terpineol (terpineol), dihydroterpineol, terpineol acetate, borneol, geraniol, linalool and the like. Examples of the aliphatic hydrocarbon-based organic solvent include n-decane, n-dodecane, and mineral spirit. These organic solvents may be used alone or in combination of two or more.

[Binder resin]
The binder resin is not particularly limited, but for example, it has a structure selected from a cellulose structure, a cellulose ester structure, and a cellulose ether structure, and a functional group (acid group) such as a carboxyl group is introduced, but at least one. Seeds can be included.

[Other]
The nickel paste according to the present embodiment may contain various additives as necessary, as long as its action is not impaired.

Specifically, a dispersant for further improving the dispersibility of the nickel powder in the paste, a viscosity adjusting agent for adjusting the viscosity, a rheology control agent for increasing the thixo property, and the like can be added.

≪2. Nickel paste manufacturing method ≫
Next, an example of a method for producing a nickel paste will be described. The method for producing nickel paste according to this embodiment has at least the following three steps [A] to [C].
That is, the method for producing this nickel paste is
[A] A nickel organic slurry step of adding an organic solvent and a polymer dispersant to a nickel powder water slurry to form a nickel organic slurry.
[B] A water separation step of separating the aqueous layer from the nickel organic slurry separated into the aqueous layer and the organic layer to obtain an organic layer nickel organic slurry.
[C] Organic layer A kneading step of adding a binder resin to a nickel organic slurry and kneading it.
have. Each step will be described in detail below.

<[A] Nickel organic slurry forming step>
In the step [A], an organic solvent and a polymer dispersant are added to a nickel powder water slurry (nickel powder water slurry), and the mixture is stirred and mixed to obtain a nickel organic slurry.

(Nickel powder water slurry)
As described above, various nickel powders can be used regardless of the manufacturing method such as a wet method or a dry method. For example, a so-called wet method such as a wet reducing method using a reducing agent such as hydrazine can be used. It is preferable to use nickel powder according to the above.

Further, as the nickel powder, it is preferable to use ultrafine nickel powder having an average particle size of 0.05 μm to 0.5 μm produced by a wet method. Ultrafine nickel powder having an average particle size of 0.05 μm to 0.5 μm is suitably used for internal electrodes of multilayer ceramic capacitors, and by using such nickel powder, the effect becomes more remarkable.

In the step [A], a nickel powdered aqueous slurry can be obtained by dispersing such ultrafine nickel powder in water by a conventionally known method.

The nickel content in the nickel powdered water slurry is not particularly limited, but is preferably 20% by mass to 75% by mass. If the content is less than 20% by mass, the water content becomes too large, and a large amount of the organic solvent used to obtain the nickel organic slurry is also used. Moreover, since the nickel concentration is low, it becomes difficult to produce a good nickel paste. On the other hand, when the content exceeds 75% by mass, the water content becomes small, the separation from the organic solvent becomes insufficient, and the water content tends to remain.

(Nickel organic slurry)
In step [A], first, an organic solvent and a polymer dispersant are mixed to obtain an organic solution. Next, the nickel organic slurry is obtained by mixing this organic solution with the nickel powdered water slurry.

Here, in the production method according to the present embodiment, the polymer dispersant having a specific structure and the amount of the polymer dispersant added are important. By adjusting the amount of the polymer dispersant having the specific structure described above to be 2 parts by mass to 10% by mass with respect to 100 parts by mass of the nickel powder, the polymer is dispersed on the surface of the nickel powder. The agent can be coated evenly.

When the polymer dispersant is coated on the nickel powder, the mixing and stirring method of the organic solution in which the polymer dispersant is dissolved and the nickel powder water slurry is not particularly limited, and for example, a known dispersion treatment is used. A method using an apparatus such as a ball mill, a homogenizer, a dairy pot, an automatic dairy pot, a kneader, or a planetary mixer can be used. Further, if necessary, the pressure may be reduced by a vacuum pump or an aspirator to perform defoaming or dehydration treatment. Further, heating and cooling treatments may be performed.

<[B] Water separation step>
In step [B], the aqueous layer is separated from the nickel organic slurry separated into the aqueous layer and the organic layer to obtain an organic layer nickel organic slurry.

When a nickel organic slurry is obtained by mixing and stirring in the above-mentioned step [A], the nickel powder in the nickel organic slurry is dispersed and transferred to the organic layer. Therefore, an organic layer nickel organic slurry can be obtained by separating and removing the supernatant water by a conventionally known method.

About 15% by mass to 50% by mass of water remains in the organic layer nickel organic slurry separated in this step, but in the production method according to the present embodiment, this residual water is also the kneading step of the next step. In [C], it can be effectively removed and reduced.

<[C] Kneading process>
In step [C], a binder resin is added to the organic layer nickel organic slurry and kneaded. In this step [C], the water remaining in the slurry can be effectively separated and removed by a so-called flushing process in which the organic layer nickel organic slurry and the binder resin are kneaded. Thereby, specifically, a nickel paste having a water content of less than 1% by mass measured by the Karl Fischer method can be obtained.

The binder resin is not particularly limited, but it is preferably added as a vehicle obtained by dissolving the resin in an organic solvent. Here, the vehicle is obtained by dissolving the resin in an organic solvent, and the organic solvent may be one usually used for the purpose of conductive paste.

For example, as the resin, a resin containing at least one selected from the group consisting of compounds having a cellulose structure, a cellulose ester structure, and a cellulose ether structure can be used. The organic solvent is not particularly limited as long as it can dissolve the above-mentioned resin, and for example, a terpene alcohol-based solvent, an aliphatic hydrocarbon-based solvent, or the like is preferable, and the above-mentioned step [A]. ], The same as the organic solvent used in the nickel organic slurry forming step is preferably used.

The concentration of the vehicle to be used is not particularly limited, but is preferably 5% by mass or more, and more preferably 10% by mass or more. If the concentration is less than 5% by mass, the viscosity becomes low, torque is less likely to be applied during kneading, water separation is insufficient, and the residual water content of the nickel paste may increase. The upper limit of the vehicle concentration is not particularly limited, but can be, for example, 30% by mass or less.

Further, as a kneading method, a known method can be used, and specifically, a method using a kneading device such as a roll mill, a ball mill, a homogenizer, a Raikai machine, a kneader, or a planetary mixer can be used. Not limited. Further, if necessary, the pressure may be reduced by a vacuum pump or an aspirator to perform defoaming or dehydration treatment. It is also possible to perform heating and cooling treatments.

In this way, by applying the "flushing process" in which the organic solvent and resin are forcibly adsorbed on the nickel water slurry to replace and separate the water with the organic solvent, the water content of the obtained nickel paste is more effective. Can be reduced.

Here, when the nickel paste is produced under the conditions of the production method according to the present embodiment, the entire amount of the compounded polymer dispersant is contained in the nickel paste.

The nickel paste obtained as described above may be mixed with, for example, barium titanate as a dielectric component of the multilayer ceramic capacitor after separating and removing the residual water. Further, a dispersant such as a surfactant can be added to improve the dispersibility, and an organic solvent can be added to adjust the viscosity. In addition, a rheology control agent or the like can be added and kneaded in order to obtain a thixo property.

As described above, in the production method according to the present embodiment, one kind selected from polyester, polyamide, polyurethane, and polyoxyalkylene as a lipophilic group having a phosphoric acid group as a hydrophilic group with respect to nickel powder. The surface is coated with the polymer dispersant having the above. According to this, a nickel paste in which nickel powder is dispersed in a state of less agglomeration can be obtained, and the occurrence of sheet attack when used as an internal electrode of a multilayer ceramic capacitor can be effectively prevented.

Then, according to the nickel paste thus obtained, it can be suitably used as a material for an internal electrode of a highly multilayer ceramic capacitor, for which there is an increasing demand for miniaturization.

Hereinafter, examples of the present invention will be described in more detail, but the present invention is not limited to the following examples.

≪Evaluation method≫
The nickel paste obtained under the production conditions shown in Test Examples 1 to 3 below was evaluated by the following evaluation method.

(Evaluation of seat attack)
The sheet attack of nickel paste was evaluated as follows.

First, the nickel paste for the internal electrode of this test example was screen-printed on a ceramic green sheet. For printing, a screen with a pattern of 325 mesh and 1.8 × 1.8 cm was used. After printing, the sheet was dried at 85 ° C. for 10 minutes, and then visually confirmed whether the sheet had holes or wrinkles due to dissolution and swelling.

In Table 1 below, those with no holes or wrinkles on the sheet are indicated by "◎", and those with some holes or wrinkles on the sheet are indicated with "Δ".

(Measurement of residual water content)
The moisture content of the obtained nickel paste was measured by measuring the residual moisture content (mass%) at 180 ° C. using a coulometric titration type Karl Fischer titer (manufactured by Kyoto Denshi Kogyo Co., Ltd.).

(Measurement of dry film density)
The obtained nickel paste was applied onto a PET film to a thickness of 200 μm using an applicator, dried at 120 ° C. for 40 minutes, and the obtained dried film was cut out so as to have a diameter of 40 mm. And the weight were measured, and the dry film density was calculated from these data.

(Evaluation of viscosity)
The obtained nickel paste was measured for viscosity (Pa · s) at ^{a shear rate of 4.0 s -1} and 25 ° C. using a rheometer (MCR-501, manufactured by Anton Pearl Co., Ltd.).

(Evaluation of surface roughness)
The obtained nickel paste was applied onto a PET film to a thickness of 200 μm using an applicator, dried at 120 ° C. for 40 minutes, and the obtained dried film was subjected to a surface roughness measuring machine (SURFCOM, manufactured by Tokyo Seimitsu Co., Ltd.). ) Was used to measure the average surface roughness Ra (μm).

<< Preparation of Nickel Paste in Examples 1 to 8 and Comparative Examples 1 to 3 >>
[Example 1]
(1) Preparation of Nickel Paste First, 90 g of nickel ultrafine powder manufactured by Sumitomo Metal Mining Co., Ltd. (product name: NR707, Ni ultrafine powder by wet reduction method, average particle size 0.07 μm, specific surface area 9.6 m ² / g) Was mixed with water to prepare 300 g of a nickel powdered water slurry (water content 70%) having a slurry concentration of 30% by mass. The average particle size of the nickel ultrafine powder was measured by an imaging method.

Next, 10.5 g of dihydroterpineol (manufactured by Nippon Kaoru Co., Ltd.) was prepared as an organic solvent, and the organic solvent had a phosphate group as a hydrophilic group and a polyamide as a lipophilic group (Japan). 2.1 g of a polymer dispersant organic solution manufactured by Lubrizol, trade name: SOLPERSE36000, weight average molecular weight: 36000) was dissolved to prepare 12.6 g of a polymer dispersant organic solution.

Then, 12.6 g of the prepared polymer dispersant organic solution was added to 300 g of the nickel powdered water slurry, and the mixture was mixed and stirred with an Excel autohomogenizer (manufactured by Nippon Seiki Co., Ltd.) at a rotation speed of 10 m / s for 2 minutes. A nickel powder organic slurry obtained by coating a nickel powder with a polymer dispersant was obtained.

Next, ethyl cellulose (manufactured by Dow Chemical Co., Ltd., standard name: STD300) was added to the organic solvent dihydroterpineol and heated to 80 ° C. with stirring to prepare a vehicle (10.5% by mass ethyl cellulose). .. Then, 21.5 g of the vehicle and the nickel powder organic slurry prepared as described above in which the nickel powder is coated with the polymer dispersant are sufficiently kneaded using three rolls, and then dihydroterpineol and minerals are sufficiently kneaded. Diluted with spirits or the like to obtain a nickel paste having a nickel concentration of 60% by mass and containing 2.3 parts by mass of a polymer dispersant with respect to 100 parts by mass of nickel powder.

(2) Evaluation of nickel paste For the obtained nickel paste, "evaluation of sheet attack", "residual moisture content", "dry film density", "viscosity", and "surface roughness" were evaluated by the above-mentioned evaluation method. Measured and evaluated.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual moisture content of the nickel paste was extremely low at 1% by mass, and the dry film density was as high as ^{5.4 g / cm 3.} The viscosity was 94.0 Pa · s, and the surface roughness Ra of the dried film was 0.04 μm.

[Example 2]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. Then, 3.2 g of a polymer dispersant having a phosphoric acid group as a hydrophilic group and a polyamide as a lipophilic group (manufactured by Nippon Lubrizol, trade name: SOLPERSE36000, weight average molecular weight: 36000) is added to the organic solvent. It was dissolved to prepare 13.7 g of an organic solution of a polymer dispersant.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual moisture content of the nickel paste was extremely low at 1% by mass, and the dry film density was as high as ^{5.1 g / cm 3.} The viscosity was 85.0 Pa · s, and the surface roughness Ra of the dried film was 0.05 μm.

[Example 3]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. A polymer dispersant having a phosphoric acid group as a hydrophilic group and a polyester as a lipophilic group in the organic solvent (manufactured by Big Chemie Japan, trade name: DISPER BYK-110, weight average molecular weight: 1000) 2 .7 g was dissolved to prepare 13.2 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual water content of the nickel paste was extremely low at 1% by mass, and the dry film density was as high as ^{5.2 g / cm 3.} The viscosity was 86.3 Pa · s, and the surface roughness Ra of the dried film was 0.04 μm.

[Example 4]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. A polymer dispersant having a phosphoric acid group as a hydrophilic group and a polyester as a lipophilic group in the organic solvent (manufactured by Big Chemie Japan, trade name: DISPER BYK-111, weight average molecular weight: 1000) 2 .4 g was dissolved to prepare 12.9 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual water content of the nickel paste was extremely low at 1% by mass, and the dry film density was as high as ^{5.2 g / cm 3.} The viscosity was 84.9 Pa · s, and the surface roughness Ra of the dried film was 0.05 μm.

[Example 5]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. A polymer dispersant having a phosphoric acid group as a hydrophilic group and a polyester as a lipophilic group in the organic solvent (manufactured by Big Chemie Japan, trade name: DISPER BYK-181, weight average molecular weight: 2000) 2 .2 g was dissolved to prepare 12.7 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual moisture content of the nickel paste was extremely low at 1% by mass, and the dry film density was as high as ^{5.0 g / cm 3.} The viscosity was 86.4 Pa · s, and the surface roughness Ra of the dried film was 0.05 μm.

[Example 6]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. Then, 3.0 g of a polymer dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prysurf A212C) having a phosphoric acid group as a hydrophilic group and a polyoxyalkylene as a lipophilic group is dissolved in the organic solvent. To prepare 13.0 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual moisture content of the nickel paste was as low as 1.0% by mass, and the dry film density was as high as ^{5.2 g / cm 3.} The viscosity was 87.0 Pa · s, and the surface roughness Ra of the dried film was 0.05 μm.

[Example 7]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. Then, 3.0 g of a polymer dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Prysurf A208F) having a phosphoric acid group as a hydrophilic group and a polyoxyalkylene as a lipophilic group is dissolved in the organic solvent. To prepare 13.0 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual moisture content of the nickel paste was as low as 1.0% by mass, and the dry film density was as high as ^{5.2 g / cm 3.} The viscosity was 84.3 Pa · s, and the surface roughness Ra of the dried film was 0.04 μm.

[Example 8]
10. 300 g of nickel powder water slurry obtained from 90 g of nickel ultrafine powder (average particle size 0.07 μm) manufactured by Sumitomo Metal Mining Co., Ltd. and dihydroterpineol (manufactured by Nippon Kaori Co., Ltd.) as an organic solvent in the same manner as in Example 1. 5g was prepared. Then, 2.5 g of a polymer dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Plysurf AL) having a phosphoric acid group as a hydrophilic group and a polyoxyalkylene as a lipophilic group is dissolved in the organic solvent. To prepare 12.5 g of a polymer dispersant organic solution.

Then, a nickel paste was obtained in the same manner as in Example 1. The obtained nickel paste was evaluated in the same manner as in Example 1.

As a result, it was possible to visually confirm that the sheet had no holes or wrinkles due to dissolution and swelling, and no sheet attack was confirmed. The residual water content of the nickel paste was as low as 0.8% by mass, and the dry film density was as high as ^{5.0 g / cm 3.} The viscosity was 81.6 Pa · s, and the surface roughness Ra of the dried film was 0.05 μm.

[Comparative Example 1]
Under the conditions of Example 1, 2.1 g of a polymer dispersant (manufactured by Nippon Lubrizol, trade name: SOLPERSE36000) and N-oleyl-N-methylglycine (manufactured by Nikko Co., Ltd., trade name: oleoil zarcosin) 221P) A nickel paste was obtained in the same manner as in Example 1 except that it was changed to 2.1 g, and the obtained nickel paste was evaluated in the same manner.

As a result, the residual water content of the nickel paste was as low as 0.7% by mass, and the dry film density was as high as ^{5.4 g / cm 3.} The viscosity was 90.0 Pa · s, and the surface roughness Ra of the dried film was 0.03 μm, and these results were equivalent to those of Examples 1 to 8. On the other hand, in Comparative Example 1, it was visually confirmed that the sheet had wrinkles and the like due to dissolution and swelling.

[Comparative Example 2]
Examples except that 2.1 g of a polymer dispersant (manufactured by Nippon Lubrizol Co., Ltd., trade name: SOLPERSE36000) was not used under the conditions of Example 1 and 2.1 g of sodium hexametaphosphate was used instead. A nickel paste was obtained in the same manner as in 1, and the obtained nickel paste was evaluated in the same manner.

As a result, the residual moisture content of the nickel paste was as high as 10.5% by mass, and the dry film density was as low as ^{4.3 g / cm 3.} The viscosity was 105.4 Pa · s, the surface roughness Ra of the dried film was 0.40 μm, and a paste having the desired characteristics could not be obtained.

[Comparative Example 3]
Examples except that 2.1 g of a polymer dispersant (manufactured by Nippon Lubrizol Co., Ltd., trade name: SOLPERSE36000) was not used under the conditions of Example 1 and 2.1 g of sodium pyrophosphate was used instead. A nickel paste was obtained in the same manner as in 1, and the obtained nickel paste was evaluated in the same manner.

As a result, the residual moisture content of the nickel paste was as high as 15.1% by mass, and the dry film density was as low as ^{4.5 g / cm 3.} The viscosity was 111.3 Pa · s, the surface roughness Ra of the dried film was 0.55 μm, and a paste having the desired characteristics could not be obtained.

Table 1 summarizes the evaluation results of Examples and Comparative Examples.

As can be seen from the results in Table 1, the nickel pastes obtained in Examples 1 to 8 can reliably prevent the occurrence of sheet attack as compared with Comparative Example 1, and are suitable as nickel pastes for internal electrodes of highly multilayer ceramic capacitors. It turned out that it can be used for.

Claims (4)

Nickel paste used for the internal electrodes of multilayer ceramic capacitors.
It contains at least nickel powder, an organic solvent, a polymer dispersant, and a binder resin.
The polymer dispersant has a phosphate group as a hydrophilic group, possess polyesters, polyamides, polyurethanes, and the one or more selected from polyoxyalkylene as lipophilic group,
The binder resin include cellulose structure, cellulose ester structure, and nickel paste have a structure selected from cellulose ether structure. The nickel paste according to claim 1, wherein the polymer dispersant is contained in a ratio of 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of nickel powder. The nickel paste according to claim 1 or 2, wherein the average particle size of the nickel powder by an imaging method is 0.05 μm or more and 0.5 μm or less. A nickel organic slurry forming step of adding an organic solvent and a polymer dispersant to a nickel powder water slurry to form a nickel organic slurry.
A water separation step of separating the aqueous layer from the nickel organic slurry separated into an aqueous layer and an organic layer to obtain an organic layer nickel organic slurry.
It has a kneading step in which a binder resin is added to the organic layer nickel organic slurry and kneaded.
A method for producing a nickel paste, wherein the polymer dispersant has a phosphoric acid group as a hydrophilic group and one or more selected from polyester, polyamide, polyurethane, and polyoxyalkylene as a lipophilic group.