WO2023100503A1 - Paste for electronic components - Google Patents

Abstract

Provided is a paste for electronic components, which contains a dispersing agent but is not needed to increase the amount of binders, and which contains a binder capable of improving the adhesion force between inorganic material particles such as nickel particles and ceramic particles.　The paste for electronic components comprises inorganic material particles (1), a dispersing agent (2), a binder (4, 5) and an organic solvent, in which the binder includes a first binder (5) that is adsorbed on the surfaces of the inorganic material particles (1) and a second binder (4) that is not adsorbed on the surfaces of the inorganic material particles (1), and at least the first binder (5) is a cellulose derivative having a single-ended carboxyl group or a single-ended carboxylic acid salt.

Description

Paste for electronic parts

The present invention relates to a paste for electronic parts containing inorganic particles, a dispersant, a binder and an organic solvent, which is used in the manufacture of electronic parts, and particularly relates to improvement of the binder.

For example, Japanese Patent Application Laid-Open No. 2018-168238 (Patent Document 1) describes an electronic component paste, that is, a conductive paste, which is useful for forming internal electrodes in a multilayer ceramic capacitor as an electronic component. This conductive paste contains a conductive powder, an organic resin (hereinafter referred to as a "binder"), an organic solvent, an additive, and a dielectric powder. The agent comprises a composition containing an unsaturated carboxylic acid-based dispersant and an oleylamine-based dispersant. In Patent Document 1, nickel powder is exemplified as the conductive powder, and ceramic powder is exemplified as the dielectric powder.

Further, in this conductive paste, the content of the unsaturated carboxylic acid-based dispersant in the additive is 0.2% by mass or more and 1.2% by mass or less with respect to the total amount of the conductive paste, and The content of the oleylamine-based dispersant in the additive is 0.3% by mass or more and 2.0% by mass or less with respect to the total amount of the conductive paste.

JP 2018-168238 A

In general, cellulose is known to have a hydroxy group on one non-reducing end side and a hydroxy group and a formyl group on the other reducing end side. Regarding ethyl cellulose as the binder described above, it can be easily assumed that most of the terminal hydroxy groups are ethoxylated due to the known manufacturing process. Therefore, it can be said that one terminal of normal ethyl cellulose (corresponding to the non-reducing terminal side of cellulose) is an ethoxy group, and the other terminal (corresponding to the reducing terminal side of cellulose) is an ethoxy group or a formyl group.

Common dispersants have alkyl chains, ether chains, or ester chains, so their adhesion to ethyl cellulose is weak. In the conductive paste, not all ethyl cellulose as a binder is adsorbed to inorganic particles such as nickel particles and ceramic particles, and some ethyl cellulose is not adsorbed to any inorganic particles.

Therefore, the adhesive force at the interface between the dispersant adsorbed on the surface of the inorganic particles and the ethyl cellulose that is not adsorbed is weakened, and as a result, between the inorganic particles in the conductive paste, more specifically, the nickel particles Adhesion between particles, between ceramic particles, or between nickel particles and ceramic particles is weakened. This tends to cause cohesive failure (separation within the internal electrode layer) between nickel particles in the internal electrodes, between ceramic particles, or between nickel particles and ceramic particles during the manufacturing process of the multilayer ceramic capacitor. There is Cohesive failure in the internal electrodes includes peeling of the internal electrode layers during pressure cutting of the laminate before firing, delamination of the multilayer ceramic capacitor after firing, and deterioration of the moisture resistance of the multilayer ceramic capacitor after baking the external electrodes. In order to cause it, it is required to prevent it from occurring as much as possible.

There is also a method to increase the amount of ethyl cellulose, which is a binder, in order to improve the adhesion between particles. However, if the amount of binder is increased, the filling rate of the nickel particles in the internal electrode coating film is decreased, resulting in decreased internal electrode coverage after firing.

On the other hand, if the conductive paste does not contain a dispersant, it is possible to eliminate interfaces with weak adhesion. However, it is difficult to ensure the dispersibility of the conductive paste without a dispersant.

Therefore, it is necessary to improve the adhesion between inorganic particles such as nickel particles and ceramic particles without increasing the amount of binder while containing a dispersant.

Therefore, an object of the present invention is to provide an electronic component paste that can satisfy the above-mentioned demands.

The present invention is directed to a paste for electronic parts containing inorganic particles, a dispersant, a binder, and an organic solvent, wherein the binder comprises a first binder adsorbed to the surface of the inorganic particles, and a second binder that is not adsorbed to the surface of the polymer, wherein at least the first binder is a cellulose derivative having one terminal carboxyl group or one terminal carboxylate.

According to the electronic component paste according to the present invention, even if the adhesive force at the interface between the dispersant adsorbed on the surface of the inorganic particles and the second binder not adsorbed on the inorganic particles is low, the inorganic particles The interface between the cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the first binder adsorbed on the surface of the inorganic particles and the second binder not adsorbed on the surface of the inorganic particles exhibits high adhesive strength at the interface. . As a result, as a whole, the adhesive strength between the inorganic particles is improved through the high adhesive strength at the interface between the first binder and the second binder as described above. Therefore, when the present invention is applied, for example, to a conductive paste for internal electrodes used in the manufacture of laminated ceramic capacitors, cohesive failure ( peeling in the internal electrode layers) can be made less likely to occur.

It is for explaining the action of the electronic component paste according to the present invention, and when it contains a comb-shaped polymer dispersant 2, (A) a state in which only the dispersant 2 is adsorbed to the inorganic particles 1, (B) an inorganic substance 1 is a diagram schematically showing a state in which a dispersing agent 2 and a first binder 5 are adsorbed to particles 1. FIG. It is for explaining the action of the electronic component paste according to the present invention, in the case where the low-molecular dispersant 3 is included, (A) the state in which only the dispersant 3 is adsorbed on the inorganic particles 1, (B) the inorganic particles 1 FIG. 2 is a diagram schematically showing a state in which a dispersant 3 and a first binder 5 are adsorbed to the surface. FIG. 1 shows ¹ H-NMR spectra of ethyl cellulose derivatized products. FIG. 2 is a diagram showing the correlation between the molecular weight of ethyl cellulose determined by NMR and that determined by GPC.

The electronic component paste according to the present invention contains inorganic particles, a dispersant, a binder, and an organic solvent. The binder includes a first binder adsorbed on the surfaces of the inorganic particles and a second binder not adsorbed on the surfaces of the inorganic particles. At least the first binder is a cellulose derivative having one terminal carboxyl group or one terminal carboxylate.

Here, the cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the first binder is the steric repulsion part of the dispersant (side chain in the case of a comb-type dispersant, main It is noted that the size is several tens to several hundred nm longer than the chain). Generally commercially available cellulose derivatives have a polystyrene equivalent molecular weight Mn of about 10000 to 90000 and a size of about 25 to 225 nm.

At the time of paste, the dispersant generally adheres to the particle surface and has a molecular chain of several nanometers (the length of the side chain in the case of a polymer dispersant and the length of the main chain in the case of a low-molecular dispersant). ), wetting with the solvent and dispersion stabilization due to steric repulsion are realized. However, at the time of drying the film, the interface between the sterically repulsive portion of several nanometers in the dispersant (the side chain in the case of a comb-shaped dispersant and the main chain in the case of a one-end adsorption dispersant) and the binder is poorly compatible. A problem arises in that the adhesive strength becomes low. This is because the molecular chains of the dispersant are arranged at narrow intervals on the particle surface to form steric repulsion sites, and steric restrictions make it difficult to develop adhesive force between the binder and the molecular chains of the dispersant. I'm assuming there is.

The above state will be described with reference to FIGS. 1 and 2. In FIG. 1A, a comb-shaped polymeric dispersant (hereinafter referred to as “polymeric dispersant”) 2 is adsorbed on the surface of inorganic particles 1 . In FIG. 2A, a low-molecular one-end adsorption dispersant (hereinafter referred to as “low-molecular-weight dispersant”) 3 is adsorbed on the surface of inorganic particles 1 . Since the polymer dispersant 2 and the low-molecular dispersant 3 form steric repulsion by arranging molecular chains at narrow intervals on the surface of the inorganic particles 1, for example, the second binder 4 made of a cellulose derivative is Adhesion between the binder and the molecular chains of dispersant 2 or 3 is difficult to develop (poor compatibility).

Here, as shown in FIGS. 1(B) and 2(B), respectively, a steric repulsion portion (comb) of the dispersant 2 or 3 is formed in the gap where the dispersant 2 or 3 is not adsorbed on the surface of the inorganic particles 1. In the case of the type polymer dispersant 2, the side chain, in the case of a single-end adsorption dispersant such as the low-molecular dispersant 3, the main chain) is longer than the main chain). When a cellulose derivative having a carboxylate is adsorbed to one end as the first binder 5, the molecular chains are arranged at wide intervals, so that steric restrictions are less likely to occur, and the second binder 4 and the first binder 5 are separated. is oriented and the adhesive force is likely to develop.

As a result, the contact between the first binder 5 and the second binder 4 increases, so that the adhesive force between the inorganic particles 1 can be improved.

In this invention, the binder that is adsorbed on the surfaces of the inorganic particles is defined as the "first binder", and the binder that is not adsorbed on the surfaces of the inorganic particles is defined as the "second binder". Therefore, the second binder can be a binder of the same composition as the first binder, ie both are cellulose derivatives with one terminal carboxyl group or one terminal carboxylate. Of course, the second binder may be a cellulose derivative that does not have a single terminal carboxyl group or a single terminal carboxylate.

It is particularly preferable that the second binder is a copolymer having a portion of a cellulose derivative (any end is acceptable) or a mixture of multiple polymers containing a cellulose derivative. A high intermolecular force acts between the one-end adsorbed cellulose derivative in the first binder and the cellulose derivative part of the second binder on the surface of the , and a high adhesive strength improvement effect is obtained.

It should be noted that the inorganic particle surface adsorption rate of the cellulose derivative having one terminal carboxyl group or one terminal carboxylate does not reach 100%. This is because the adsorption phenomenon is not completely irreversible because of single-point adsorption. The inorganic particle surface adsorption rate varies depending on the chemical state and surface area of the inorganic particle surface, the type of solvent contained in the electronic component paste, the amount and concentration of the binder added in the electronic component paste, and the like. About 30 to 90% of the added amount is adsorbed in the region where the amount is not excessive.

In summary, when the binder does not contain a cellulose derivative having one terminal carboxyl group or one terminal carboxylate, as shown in FIGS. The interface between the dispersing agent 2 or 3 adsorbed to the inorganic particles 1 and the second binder 4 made of, for example, a cellulose derivative and not adsorbed to the inorganic particles 1 is mainly an interface having only a low adhesive strength.

On the other hand, when the binder contains the first binder 5 made of a cellulose derivative having one terminal carboxyl group or one terminal carboxylate, as shown in FIGS. 1(B) and 2(B), inorganic particles 1 and the second binder 4 made of, for example, a cellulose derivative that is not adsorbed on the surface of the inorganic particles 1. A first binder 5 made of a cellulose derivative having a one-end carboxyl group or a one-end carboxylate adsorbed on the surface of the particles 1, and a second binder not adsorbed to the surfaces of the inorganic particles 1 and having, for example, a cellulose derivative portion. It will also have an interface with high adhesion between 4 and . As a result, as a whole, the adhesive force between the inorganic particles 1 is improved.

More specifically, cohesive failure is less likely to occur between metal particles, between ceramic particles, or between metal particles and ceramic particles, and this paste for electronic components is used, for example, in the production of laminated ceramic capacitors for internal electrodes. When it is applied to the conductive paste for , it is possible to prevent the peeling of the internal electrode layers from occurring particularly when cutting the laminated body before firing.

In the paste for electronic parts, the cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the first binder is 1.0 mg/m ² to 5.0 mg/m ² with respect to the total surface area of the inorganic particles. is preferred. In other words, 1.0 mg/m ² to 5.0 mg/m ² of the cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the first binder is adsorbed to the total surface area of the inorganic particles. is preferred. This is because a significant effect appears when the adsorption amount becomes 1.0 mg/m ² or more. On the other hand, there is almost no adsorption exceeding 5.0 mg/m ² .

The cellulose derivative having one terminal carboxyl group or one terminal carboxylate is preferably a cellulose ether having one terminal carboxyl group or one terminal carboxylate. This is because it is more realistic to obtain a cellulose ether having a single terminal carboxyl group or a single terminal carboxylate as a cellulose derivative having a single terminal carboxyl group or a single terminal carboxylate when considering the synthetic reaction scheme described later. be.

The cellulose ether having one terminal carboxyl group or one terminal carboxylate is more preferably at least one selected from methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylhydroxyethylcellulose and hydroxypropylmethylcellulose.

Preferably, as the dispersant contained in the electronic component paste, a comb-shaped polymer dispersant or a low-molecular one-end adsorption dispersant is used, as described above. As the comb-shaped polymeric dispersant, for example, a polycarboxylic acid-based dispersant is used. Comb-type polymer dispersants such as polycarboxylic acid-based dispersants and low-molecular one-end adsorption dispersants form steric repulsion sites by arranging molecular chains at narrow intervals on the surface of inorganic particles, resulting in steric restrictions. Therefore, there is a problem that the adhesive strength between the binder and the molecular chain of the dispersant is difficult to develop (poor compatibility). However, as described above, this problem can be advantageously solved by the cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the binder contained in the paste for electronic parts according to the present invention.

The inorganic particles contained in the electronic component paste according to the present invention preferably contain at least one of ceramic particles and metal particles. For example, a paste for forming dielectric layers in a multilayer ceramic capacitor contains at least ceramic particles, and a paste for forming internal electrode layers contains at least metal particles. The ceramic particles described above contain at least one element selected from, for example, Ba, Ti, Ca, Zr and Sr. The metal particles described above contain, for example, at least one metal selected from Cu, Ni, Au and Ag.

<<Experimental example 1>>
[Synthesis of cellulose derivative]
In this experimental example, in order to clarify the one-end carboxylated cellulose derivative and the one-end esterified cellulose derivative to be the binders contained in the paste for electronic parts, their respective synthesis methods are shown below. The synthesis method shown below is a synthesis method using ethyl cellulose, which is a kind of cellulose derivative and is widely used in pastes for electronic parts and the like. In addition, these synthesis methods are only examples, and are not limited to these.

<Method for Synthesizing Single-Terminal Carboxylated Cellulose Derivative>
(1) Formation of one-end carboxylated cellulose by oxidation reaction of reducing terminal of cellulose A 50% sodium hydroxide aqueous solution (1680 g) was added to an aqueous dispersion slurry of cellulose (solid content: 1440 g). Then, sodium anthraquinone-2-sulfonate (24 g) dissolved in 30% hydrogen peroxide is added and stirred to oxidize the reducing end of the cellulose, followed by filtration and washing with water to obtain cellulose with one end carboxylated. rice field. This reaction is a reaction of oxidizing a formyl group having a formyl group by ring-opening to a carboxyl group among the tautomerisms of the reducing ends of cellulose.

Various methods are known for the oxidation reaction of the cellulose reducing terminal and the formyl group of the ring-opened sugar.

(2) Deprotonation reaction with sodium hydroxide A 50% sodium hydroxide aqueous solution was added to an aqueous solution of one-end carboxylated cellulose, and the mixture was stirred at 60°C for 20 minutes to convert the hydroxyl group to -ONa and one end to -COONa. Alkali cellulose was obtained.

(3) Ethoxylation (Etherification) Reaction and Ethyl Esterification Reaction with Ethyl Chloride Alkali cellulose and ethyl chloride were stirred at 110° C. for 12 hours in a pressure cooker at 0.5 MPa, and Ethyl cellulose whose ends were -COONa, -COOH or -COOEt was obtained. The ethoxylation degree of substitution (DS) for the three OH groups of the cellulose monomer units obtained at this time is in the range of 2.46 to 2.58 (ethoxylation degree 48.0 to 49.5% by mass). The amount of sodium hydroxide added and the amount of ethyl chloride added were adjusted so that In this synthesis, since the etherification reaction proceeds faster than the esterification reaction, only a small amount of -COOEt is esterified.

(4) Ester hydrolysis reaction One end of ethyl cellulose -COOEt -COOEt is hydrolyzed to -COOH, and the hydroxyl group is -OEt (substitution degree 2.5) and one end is -COONa. (carboxylate) or -COOH (carboxyl group) ethyl cellulose was obtained.

There are various hydrolysis reaction conditions, but the reaction proceeds by adding water to the alcohol solvent and heating it. A catalyst may be added for efficient reaction. Since esterification is difficult to proceed during the etherification reaction using ethyl chloride, ethyl cellulose in which most of the ends are -COONa (carboxylate) or -COOH (carboxyl group) at one end can be obtained without performing this step. Obtainable.

(5) Washing and drying After removing salts and by-products by washing with hot water, dry under reduced pressure to convert one end to -COONa (carboxylate) or -COOH (carboxyl group) and to the other end. A solid of ethyl cellulose with a degree of ethoxylation substitution of 2.5 was obtained, in which the was -OEt (ether). By adjusting the number average molecular weight of the cellulose to be used first in the range of 10,000 to 100,000, the number average molecular weights are 1.3×10 ⁴ , 2.0×10 ⁴ and 5.4×10 ^{4 .} , and 8.8×10 ⁴ of ethyl cellulose could be made. The number average molecular weight was determined by GPC (gel permeation chromatography) under THF (tetrahydrofuran) solvent and converted to polystyrene.

<Method for Synthesizing Single-Terminal Esterified Cellulose Derivative>
(1) Production of one-end carboxylated cellulose by oxidation reaction of the reducing end of cellulose In the same manner as in the synthesis of one-end carboxylated cellulose derivative described above, 50% sodium hydroxide was added to the water-dispersed slurry of cellulose (solid content: 1440 g). An aqueous solution (1680 g) was added. Then, sodium anthraquinone-2-sulfonate (24 g) dissolved in 30% hydrogen peroxide is added and stirred to oxidize the reducing end of the cellulose, followed by filtration and washing with water to obtain cellulose with one end carboxylated. rice field.

(2) Deprotonation Reaction with Sodium Hydroxide As in the synthesis of the one-end carboxylated cellulose derivative, a 50% sodium hydroxide aqueous solution was added to the one-end carboxylated cellulose aqueous solution, and the mixture was stirred at 60° C. for 20 minutes. Thus, an alkali cellulose having —ONa at the hydroxyl group and —COONa at one end was obtained.

(3) Ethoxylation (Etherification) Reaction and Ethyl Esterification Reaction with Ethyl Chloride As in the synthesis of the one-end carboxylated cellulose derivative described above, alkali cellulose and ethyl chloride were heated at 110° C. in a pressure cooker at 0.5 MPa. for 12 hours to obtain an ethyl cellulose in which the hydroxyl group is —OEt and one end is —COONa, —COOH or —COOEt. The degree of substitution (DS) of ethoxylation for the OH group of the cellulose obtained at this time is in the range of 2.46 to 2.58 (degree of ethoxylation 48.0 to 49.5% by mass). The amount of sodium added and the amount of ethyl chloride added were adjusted.

Next, after removing salts and by-products by washing with hot water, it was dried under reduced pressure to obtain a solid ethyl cellulose.

(4) Esterification Reaction After the ethylcellulose solid obtained in (3) above was dissolved in ethanol, concentrated sulfuric acid was added dropwise as an acid catalyst to ethylesterify the carboxyl group at one end.

(5) Washing and drying After removing salts and by-products by washing with hot water, drying under reduced pressure resulted in -COOEt (ethyl ester group) at one end and -OEt (ether) at the other end. , a solid of ethyl cellulose having a degree of substitution of ethoxylation of 2.5 was obtained. By adjusting the number-average molecular weight of the cellulose initially used in the range of 10,000 to 100,000, the number-average molecular weights Mn are 1.4×10 ⁴ , 2.0×10 ⁴ and 5.2, respectively. Four kinds of ethyl cellulose of x10 ⁴ and 8.9 x 10 ⁴ could be made. As in the case described above, the number average molecular weight was determined by GPC in a THF solvent and converted to polystyrene.

<Quantification of Carboxyl Groups in Single-Terminal Carboxylated Ethylcellulose>
The amount of carboxyl groups in the single-end carboxylated ethyl cellulose synthesized as described above was quantified by ¹ H-NMR measurement. A trimethylsilyl (TMS) derivatization method was used because conventional NMR measurements were expected to lack sensitivity in quantifying terminal carboxyl groups, which are trace amounts.

The TMS derivatization method is a method of substituting a trimethylsilyl group (Si(CH ₃ ) ₃ ) for H of a hydroxyl group contained in a carboxyl group of ethyl cellulose. Due to this derivatization, the number of hydrogen atoms in the carboxyl group is changed from 1H to 9H, so the detection sensitivity in ¹ H-NMR is increased ninefold.

A derivatized product is obtained by adding ethyl cellulose and a derivatizing reagent (BSTFA) to a dehydrated chloroform solvent and heating at 70° C. for 1 hour. Since the derivatization reagent acts on both hydroxyl groups and carboxyl groups of ethyl cellulose, the amount of reagent to be added was about 1.5 times the molar number of hydroxyl groups and terminal carboxyl groups of ethyl cellulose. In addition, it was confirmed that the quantitative values of TMS hydroxyl groups and carboxyl groups did not change even when the amount of the reagent was added in excess of 1.5 times the molar amount. After the solution after the reaction was returned to room temperature and vacuum-dried, the solvent and unreacted derivatization reagent were removed to obtain a dried derivatized product by preparative GPC. This dried product was redissolved in deuterated chloroform, which is a solvent for NMR measurement, and ¹ H-NMR measurement was performed. A ¹ H-NMR spectrum of the ethyl cellulose derivatized product is shown in FIG.

In the ¹ H-NMR spectrum of the ethyl cellulose derivatized product, a peak derived from the derivatization of the carboxyl group is detected at 0.3 ppm indicated by the arrow in FIG. The concentration of carboxyl groups in ethyl cellulose was obtained by calculating the respective molar ratios from the peak area ratios of the cellulose skeleton, ethoxy groups, carboxyl groups, and hydroxyl groups observed by ¹ H-NMR. Table 1 shows the quantification results of carboxyl groups and the average molecular weights of the corresponding samples. GPC was measured under THF solvent, and the number average molecular weight was determined in terms of polystyrene.

The number of carboxyl groups in ethyl cellulose decreases as the molecular weight increases, suggesting that the carboxyl groups are present in sites that depend on the molecular weight. Since the terminal concentration of the polymer decreases as the molecular weight of one molecular chain increases, it is considered that the quantified carboxyl groups are present at the terminal. From the aspect of the synthesis reaction scheme of the sample, it can be determined that the carboxyl group analyzed by NMR exists at one end.

Furthermore, assuming that the carboxyl group quantified by NMR exists at one end of ethyl cellulose, the molecular weight of ethyl cellulose was calculated by determining the number of repetitions of ethyl cellulose. Table 2 shows the average molecular weight determined by NMR and the average molecular weight determined by GPC.

Since the average molecular weight determined by GPC is in terms of polystyrene, the average molecular weight determined by NMR does not match the average molecular weight determined by GPC in absolute value. On the other hand, as shown in FIG. 4, when the molecular weight values obtained by both methods were compared for samples with different molecular weights, a high correlation was shown. This result indicates that a carboxyl group exists at one end of ethyl cellulose, and it can be said that NMR quantified the carboxyl group present at one end.

[Preparation of conductive paste]
One end esterified ethyl cellulose (number average molecular weight = 2.0 × 10 ⁴ ) or one end carboxylated ethyl cellulose (number average molecular weight = 2.0 × 10 ⁴ ) of 1.1 parts by mass (2.9 mg/m ² with respect to the total surface area of the nickel powder and the ceramic powder) and 39.7 parts by mass of dihydroterpineol acetate as an organic solvent. 1 organic vehicle was obtained.

This first organic vehicle, 45.5 parts by mass of nickel powder with a BET diameter of 177 nm (SSA (specific surface area) = 3.8 m ² /g), and barium titanate with a BET diameter of 13 nm (SSA = 77 m ² /g) and 0.70 parts by mass of a polycarboxylic acid-based polymer dispersant are mixed and dispersed by a three-roll mill to obtain an intermediate conductive paste. rice field.

After that, the intermediate conductive paste, shown in the "second binder" column of Tables 3 and 4,
- Single-end esterified ethyl cellulose,
- cellulose acetate butyrate,
- Acrylic binder A (a binder made of polyisobutyl methacrylate),
・Polyvinyl butyral resin,
・Mixing of one-end esterified ethyl cellulose and polyvinyl butyral resin,
・Mixing of cellulose acetate butyrate and polyvinyl butyral resin,
- Mixing of cellulose acetate butyrate and acrylic binder A,
- Copolymer A (details will be described later),
- Copolymer B (details will be described later),
· Copolymer C (details will be described later),
- Copolymer D (details will be described later),
Copolymer E (details will be described later), and Copolymer F (details will be described later),
1.1 parts by mass of either
8.9 mass of dihydroterpineol acetate;
was added, followed by roll dispersion treatment to complete the conductive paste.

The dispersion method is not limited to the above method, and various methods such as roll mill, ball mill, bead mill, and high-pressure dispersion can be applied. This applies not only to the operation for obtaining the conductive paste here, but also to other operations.

The details of each of the copolymers A to F and the experimental procedure for obtaining the organic vehicle (binder solution) containing each of the copolymers A to F are as follows.

<Copolymer A>
Copolymer A is a copolymer of one-end carboxylated ethyl cellulose and acrylic binder B (main monomer is isobutyl methacrylate and contains 5 mol % of 2-hydroxyethyl methacrylate).

5.5 parts by mass of one-end carboxylated ethyl cellulose having a number average molecular weight Mn of 2.0×10 ⁴ and 5.5 parts by mass of the acrylic binder B having a number average molecular weight Mn of 2.1×10 ⁴ After drying under reduced pressure, 89 parts by mass of dihydroterpineol acetate was added and dissolved at 50° C. in a nitrogen atmosphere. The resulting solution was added with 1.5 mol of methacrylic acid and 2.0 mol of diisopropylcarbodiimide as a condensing agent (assuming that the total number of moles of one-end carboxylated ethyl cellulose and acrylic binder B in terms of Mn is 1 mol). , dimethylaminopyridine as a reaction accelerator in an amount 0.01 times the molar amount of the condensing agent was added, and the mixture was stirred at a temperature of 50°C for 24 hours to carry out the reaction. Thus, the introduction of methacrylate into the single-end carboxylated ethyl cellulose and the acrylic binder B, and the esterification of the hydroxyl groups possessed by the acrylic binder B and the single-end carboxylated ethyl cellulose with the carboxyl groups of the single-end carboxylated ethyl cellulose were carried out.

Next, 0.1 mol of azoisobutyronitrile (AIBN) as a polymerization initiator for the introduced methacrylate (with the total number of moles of one-end carboxylated ethyl cellulose and acrylic binder B converted to Mn being 1 mol) was mixed to obtain 70 C. for 5 hours to obtain a binder solution containing copolymer A.

¹ H-NMR of the obtained copolymer A confirmed the formation of an ester group and the ^{disappearance} of a vinyl group. It was found that the polymerization reaction had progressed because the amount increased more. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

<Copolymer B>
Copolymer B is a copolymer of one-end-esterified ethyl cellulose and polyvinyl butyral resin.

5.5 parts by mass of one-end esterified ethyl cellulose with a number average molecular weight Mn = 2.0 × 10 ⁴ and a polyvinyl acetal resin with a number average molecular weight Mn = 2.2 × 10 ⁴ having hydroxyl groups (manufactured by Sekisui Chemical Co., Ltd. 5.5 parts by mass of “BL-S”) was dried under reduced pressure, 89 parts by mass of dihydroterpineol acetate was added, and dissolved at 50° C. under a nitrogen atmosphere. The resulting solution was added with 1.5 mol of methacrylic acid and 1.5 mol of diisopropylcarbodiimide as a condensing agent (assuming that the total number of moles of one-end-esterified ethyl cellulose and polyvinyl acetal-based resin in terms of Mn is 1 mol). Then, dimethylaminopyridine as a reaction accelerator was added in an amount of 0.01 times the number of moles of the condensing agent, and the mixture was stirred at a temperature of 50°C for 24 hours to carry out a reaction. This led to the introduction of methacrylate into the hydroxyl groups of one-end-esterified ethyl cellulose and polyvinyl acetal-based resins.

Next, 0.1 mol of azoisobutyronitrile (AIBN) was mixed as a polymerization initiator for the introduced methacrylate (the total number of moles of one-end-esterified ethyl cellulose and polyvinyl acetal resin converted to Mn being 1 mol). A reaction was carried out at 70° C. for 5 hours to obtain a binder solution containing copolymer B.

¹ H-NMR of the obtained copolymer B confirmed the formation of an ester group and the ^{disappearance} of a vinyl group. It was found that the polymerization reaction had progressed because the amount increased more. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

<Copolymer C>
Copolymer C is a copolymer of one-end carboxylated ethyl cellulose and polyvinyl butyral resin.

5.5 parts by mass of one-end carboxylated ethyl cellulose with a number average molecular weight Mn = 2.0 × 10 ⁴ and a polyvinyl acetal resin with a number average molecular weight Mn = 2.2 × 10 ⁴ having hydroxyl groups (manufactured by Sekisui Chemical Co., Ltd. 5.5 parts by mass of “BL-S”) was dried under reduced pressure, 89 parts by mass of dihydroterpineol acetate was added, and dissolved at 50° C. under a nitrogen atmosphere. The resulting solution was added with 1.5 mol of methacrylic acid and 2.0 mol of diisopropylcarbodiimide as a condensing agent (where the total number of moles of one-end carboxylated ethyl cellulose and polyvinyl acetal-based resin in terms of Mn is 1 mol). and dimethylaminopyridine as a reaction accelerator in an amount 0.01 times the number of moles of the condensing agent were added, and the mixture was stirred at a temperature of 50° C. for 24 hours to carry out a reaction. As a result, methacrylate is introduced into the hydroxy groups of the one-end carboxylated ethyl cellulose and the polyvinyl acetal-based resin, and the hydroxy groups of the polyvinyl acetal-based resin and the one-end carboxylated ethyl cellulose are esterified with the carboxyl groups of the one-end carboxylated ethyl cellulose. and proceeded.

Next, 0.1 mol of azoisobutyronitrile (AIBN) was mixed as a polymerization initiator for the introduced methacrylate (the total number of moles of one-end carboxylated ethyl cellulose and polyvinyl acetal resin converted to Mn being 1 mol). A reaction was carried out at 70° C. for 5 hours to obtain a binder solution containing copolymer C.

From ¹ H-NMR of the obtained copolymer C, the formation of ester groups and the disappearance of vinyl groups could be confirmed, and the number average molecular weight before the reaction was 2.6 × 10 ⁴ . It was found that the polymerization reaction had progressed because the amount increased more. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

<Copolymer D>
Copolymer D is a copolymer of one-end carboxylated ethyl cellulose and polyvinyl butyral resin.

5.5 parts by mass of one-end carboxylated ethyl cellulose with a number average molecular weight Mn = 2.0 × 10 ⁴ and a polyvinyl acetal resin with a number average molecular weight Mn = 2.2 × 10 ⁴ having hydroxyl groups (manufactured by Sekisui Chemical Co., Ltd. 5.5 parts by mass of “BL-S”) was dried under reduced pressure, 89 parts by mass of dihydroterpineol acetate was added, and dissolved at 50° C. under a nitrogen atmosphere. To the resulting solution, 1.1 mol of diisopropylcarbodiimide as a condensing agent (assuming that the number of moles of one-end carboxylated ethyl cellulose in terms of Mn is 1 mol) and dimethylaminopyridine as a reaction accelerator were added to 0 moles of the condensing agent. was added, and the reaction was carried out by stirring at a temperature of 50° C. for 24 hours. As a result, a binder solution containing polyvinyl acetal-based resin and a copolymer D obtained by esterification of the hydroxyl group of the one-end carboxylated ethyl cellulose and the carboxyl group of the one-end carboxylated ethyl cellulose was obtained.

¹ H-NMR of the resulting copolymer confirmed the formation of ester groups, and the number average molecular weight Mn was 2.4×10 ⁴ , which was higher than the number average molecular weight before the reaction. From this, it was found that the polymerization reaction proceeded. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

<Copolymer E>
Copolymer E is a copolymer of cellulose acetate butyrate and polyvinyl butyral resin.

5.5 parts by mass of cellulose acetate butyrate (“CAB381-0.1” manufactured by Eastman) having a number average molecular weight Mn of 2.0×10 ⁴ and polyvinyl having a number average molecular weight Mn of 2.2×10 ⁴ 5.5 parts by mass of acetal resin (“BL-S” manufactured by Sekisui Chemical Co., Ltd.) was dried under reduced pressure, and 89 parts by mass of dihydroterpineol acetate was added and dissolved at 50° C. under a nitrogen atmosphere. The resulting solution was added with 2 mol of methacrylic acid (where the total number of moles of cellulose acetate butyrate and polyvinyl acetal-based resin in terms of Mn is 1 mol), 2 mol of diisopropylcarbodiimide as a condensing agent, and a reaction accelerator. Then, dimethylaminopyridine was added in an amount 0.01 times the molar amount of the condensing agent, and the mixture was stirred at a temperature of 50° C. for 24 hours to carry out a reaction. This led to the introduction of methacrylate into cellulose acetate butyrate and polyvinyl acetal resins.

Next, 0.1 mol of azoisobutyronitrile (AIBN) as a polymerization initiator for the introduced methacrylate (the total number of moles of cellulose acetate butyrate and polyvinyl acetal resin converted to Mn being 1 mol) is mixed, A reaction was carried out at 70° C. for 5 hours to obtain a binder solution containing copolymer E.

¹ H-NMR of the resulting copolymer confirmed the formation of an ester group and the ^{disappearance} of a vinyl group. It was found that the polymerization reaction proceeded from the fact that it had increased. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

<Copolymer F>
Copolymer F is a copolymer of cellulose acetate butyrate and acrylic binder B (main monomer is isobutyl methacrylate and contains 5 mol % of 2-hydroxyethyl methacrylate).

5.5 parts by mass ^{of cellulose acetate butyrate (“CAB381-0.1” manufactured by Eastman) having a number average molecular weight Mn of 2.0×10 4 and} the above-mentioned 5.5 parts by mass of acrylic binder B was dried under reduced pressure, 89 parts by mass of dihydroterpineol acetate was added, and dissolved at 50° C. in a nitrogen atmosphere. The resulting solution was added with 2 mol of methacrylic acid (where the total number of moles of cellulose acetate butyrate and polyvinyl acetal-based resin in terms of Mn is 1 mol), 2 mol of diisopropylcarbodiimide as a condensing agent, and a reaction accelerator. Then, dimethylaminopyridine was added in an amount 0.01 times the molar amount of the condensing agent, and the mixture was stirred at a temperature of 50° C. for 24 hours to carry out a reaction. In this way, introduction of methacrylate into cellulose acetate butyrate and acrylic binder B was advanced.

Next, 0.1 mol of azoisobutyronitrile (AIBN) as a polymerization initiator for the introduced methacrylate (the total number of moles of cellulose acetate butyrate and polyvinyl acetal-based resin in terms of Mn being 1 mol) was mixed to obtain 70 C. for 5 hours to obtain a binder solution containing copolymer F.

¹ H-NMR of the obtained copolymer confirmed the formation of ester groups and the disappearance of vinyl groups, and the number average molecular weight Mn was 2.4 × 10 ⁴ . It was found that the polymerization reaction proceeded from the fact that it had increased. The number average molecular weight was determined by GPC under THF solvent and converted to polystyrene.

[Evaluation of Binder Adsorption Amount of Conductive Paste]
The following operation was carried out for the produced conductive paste, and the adsorption amount of the binder was evaluated.

400 cc of acetone was added to 200 cc of the conductive paste, and after stirring with a planetary mixer for 30 minutes, it was treated with a centrifuge ("CS100FNX" manufactured by himac) at 29000 rpm for 15 minutes to obtain nickel powder. and ceramic powder were precipitated, and the supernatant was collected. Since the collected supernatant contains unadsorbed binder, the concentration of organic solids in the entire supernatant was calculated from the change in weight during drying. The total organic solid content in the conductive paste was calculated from the change in weight when the dried paste was heated to 1000° C. with a TG-DTA (thermogravimetric differential thermal analyzer) in an N ₂ atmosphere.

By applying the values obtained above to the following formula, the amount of binder adsorption relative to the total surface area of nickel powder and ceramic powder was obtained.

Amount of adsorbed binder = (total amount of organic solids - total amount of organic solids in supernatant - total amount of dispersant) / total surface area of nickel powder and ceramic powder. Since it is used, it is in an adsorption state that can be regarded as substantially irreversible, and the calculation was made on the assumption that the supernatant does not contain the dispersant.

The obtained binder adsorption amounts are shown in Tables 3 and 4 in the column "Binder adsorption amount with respect to the total surface area of nickel powder and ceramic powder".

[Evaluation of Binder Adsorbed Amount and Adsorbed Material of Conductive Paste]
For Comparative Example 1-1 and Example 1-1, the following evaluation (1) and evaluation (2) were additionally performed in order to evaluate the adsorbed amount and adsorbed substances of the binder.

<Evaluation (1)>
After adding 400 cc of acetone to 200 cc of the conductive paste and stirring with a planetary mixer for 30 minutes, it was treated with a centrifuge (“CS100FNX” manufactured by himac) for 15 minutes at 33000 rpm, and nickel powder and The ceramic powder was precipitated and the supernatant was collected. The collected supernatant was dried, and the dried solid content of the obtained supernatant (that is, unadsorbed binder) was converted to TMS and subjected to NMR measurement to identify the unadsorbed binder. In addition, when the supernatant contains multiple types of binders or dispersants, it is necessary to perform fractionation by HPLC (high performance liquid chromatograph).

<Evaluation (2)>
400 cc of acetone was added to the solid content precipitated by the centrifugal separation of evaluation (1), and agitation was performed for 30 minutes at 12,000 rpm using a homomixer "MARK II" manufactured by Primix Co., Ltd., which adsorbed onto the particle surface. A part of the binder contained in the film was desorbed and adsorbed.

Then, the mixture was centrifuged (“CS100FNX” manufactured by himac) for 15 minutes at 29000 rpm to precipitate nickel powder and ceramic powder, and the supernatant was collected. The collected supernatant was dried, and the dried solid content of the obtained supernatant was converted to TMS and subjected to NMR measurement to identify the adsorbent binder. In addition, when multiple types of binders or dispersants are included, fractionation by HPLC is required.

As a result, in Comparative Example 1-1, one-end esterified ethyl cellulose was detected in both Evaluation (1) and Evaluation (2), while in Example 1-1, Evaluation (1) resulted in one-end Esterified ethyl cellulose and one-end carboxylated ethyl cellulose were detected at a ratio of (single-end esterified ethyl cellulose):(single-end carboxylated ethyl cellulose) = 3:1. Terminal carboxylated ethyl cellulose was detected at a ratio of (single-terminal esterified ethyl cellulose):(single-terminal carboxylated ethyl cellulose)=1:7. From this, it was determined that a paste in which the one-end carboxylated ethyl cellulose was adsorbed on each surface of the nickel particles and the ceramic particles was produced.

[Preparation of unfired laminate chip]
A ceramic material mainly composed of barium titanate with a BET diameter of 150 nm, a polyvinyl butyral resin, a solvent of toluene and echinene in a ratio of 5:5, and a plasticizer, triethylene glycol di(2-ethylhexanoate). , were mixed at a predetermined ratio and subjected to wet dispersion treatment using a bead mill to obtain a ceramic slurry.

Next, this ceramic slurry was formed on a PET (polyethylene terephthalate) film using a doctor blade method so as to have a thickness of 1.0 μm after drying to obtain a ceramic green sheet.

Next, on the ceramic green sheet, a pattern was formed on the ceramic green sheet so that the chip-shaped laminated body to be obtained later after cutting and firing had a planar dimension of 1.0 mm×0.5 mm. Conductive paste according to the above sample so that 30 μm (X-ray fluorescence analysis (XRF) measurement) and an average physical thickness of 0.60 μm (focused ion beam (FIB) processing cross-section scanning electron microscope (SEM) observation) It was printed by a screen printer to form a conductive paste coating film to serve as an internal electrode.

Next, after peeling each ceramic green sheet from the PET film, first, 50 ceramic green sheets not printed with a conductive paste coating were stacked, and then 350 sheets printed with a conductive paste coating. The laminated structure obtained by stacking the ceramic green sheets and further stacking 30 ceramic green sheets without the conductive paste coating film printed thereon was placed in a predetermined mold. Then, the laminate structure in the mold was pressed to obtain an unfired laminate. The obtained unfired laminate was heated to 90° C. and cut into a predetermined size by pressing to obtain an unfired laminate chip.

[Evaluation of Occurrence of Structural Defects]
For each of 100 unfired laminate chips randomly selected from the above unfired laminate chips, the cut surface of the press cut was observed with an optical microscope, and cohesive failure in the conductive coating film as a structural defect (internal The presence or absence of peeling in the electrode layer was confirmed.

The column "number of structural defects" in Tables 3 and 4 shows the number of laminate chips in which structural defects were observed among the 100 laminate chips. Based on the number of laminate chips in which structural defects were observed, occurrence of structural defects was evaluated according to the following criteria.
A: The number of laminates in which structural defects were observed was 0 or 1.
○: The number of laminates in which structural defects were observed was 2 or more and 5 or less.
x: The number of laminates in which structural defects were observed is 6 or more.

From the comparison between Comparative Examples 1-1 to 1-13 shown in Table 3 and Examples 1-1 to 1-13 shown in Table 4, the single-end carboxylated ethyl cellulose as the first binder was mixed with nickel particles and ceramic particles. It can be seen that the number of structural defects can be greatly reduced by adsorbing to , regardless of the type of binder added as the second binder.

High-molecular-weight comb-type dispersants such as polycarboxylic acid-based dispersants and low-molecular-weight single-end-adsorbed dispersants form steric repulsion sites by arranging molecular chains at narrow intervals on the surface of inorganic particles. Due to restrictions, there is a problem that it is difficult to develop an adhesive force (poor compatibility) between the binder and the molecular chains of the dispersant. On the other hand, when one-end carboxylated ethyl cellulose of high molecular weight is adsorbed on the surface of inorganic particles, the molecular chains are arranged at wide intervals, so that steric restrictions are less likely to occur, and the binder and one-end carboxylated It is considered that the adhesive strength with ethyl cellulose is easily expressed (compatibility is easily achieved).

In addition, from the comparison between Examples 1-5 to 1-7 and Examples 1-8 to 1-13, it was found that, as in Examples 1-5 to 1-7, the cellulose derivative was mixed and included, and the As in Examples 1-8 to 1-13, it is found that the use of a copolymer having a cellulose derivative portion as a binder is more effective in suppressing structural defects. This is presumed to be due to the fact that in the different binder mixed systems such as those of Examples 1-5 to 1-7, the adhesion at the interfaces of the different binders was weak, and cohesive failure (peeling within the internal electrode layers) occurred starting there. be done.

In addition, from the comparison between Examples 1-1 to 1-2 and Examples 1-8 to 1-13, the cellulose derivative having a higher Tg than the composition of only the cellulose derivative having a high Tg (glass transition point) and a different binder having a low Tg is softer and less likely to break.

<<Experimental example 2>>
In Experimental Example 2, the amount of binder adsorption and occurrence of structural defects were evaluated in the same manner as in Experimental Example 1 for samples in which the composition of the organic vehicle in the conductive paste was changed.

[Preparation of conductive paste]
In order to obtain Examples 2-1 to 2-4 shown in Table 5, 45.5 parts by mass of nickel powder having a BET diameter of 177 nm (SSA = 3.8 m ² /g) and a BET diameter of 13 nm (SSA = 77 m ² 3.0 parts by mass of a ceramic powder containing barium titanate as a main component, 0.70 parts by mass of a polycarboxylic acid-based polymer dispersant, and a number average molecular weight of 2.0× as a first binder. 10 ⁴ one-end carboxylated ethyl cellulose was mixed with 39.7 parts by mass of dihydroterpineol acetate as an organic solvent in the parts by mass shown in the column of "first binder" in Table 5, and the mixture was subjected to roll dispersion treatment. , to obtain an intermediate conductive paste.

After that, to this intermediate conductive paste, the above-mentioned copolymer C as a second binder was added in the parts by mass shown in the "second binder" column of Table 5, and 8.9 parts by mass of dihydroterpineol acetate. were added and dispersed by a three-roll mill to obtain conductive pastes according to Examples 2-1 to 2-4 shown in Table 5.

On the other hand, in order to obtain Example 2-5 shown in Table 5, 45.5 parts by mass of nickel powder with a BET diameter of 177 nm (SSA = 3.8 m ² /g) and a BET diameter of 13 nm (SSA = 77 m ² /g) ), 3.0 parts by mass of a ceramic powder containing barium titanate as a main component, 0.70 parts by mass of a polycarboxylic acid-based polymer dispersant, and a number average molecular weight of 2.0 × 10 ⁴ as a first binder. 1.6 parts by mass of one-end carboxylated ethyl cellulose and 39.2 parts by mass of dihydroterpineol acetate were mixed and subjected to roll dispersion treatment to obtain an intermediate conductive paste.

After that, 1.1 parts by mass of one-end carboxylated ethyl cellulose having a number average molecular weight of 2.0×10 ⁴ and 8.9 parts by mass of dihydroterpineol acetate are added as a second binder to this intermediate conductive paste. Then, a dispersion treatment was performed using a three-roll mill to obtain a conductive paste according to Example 2-5 shown in Table 5.

[Evaluation of Binder Adsorption Amount and Structural Defect Occurrence]
In the same manner as in Experimental Example 1, the amount of adsorbed binder with respect to the total surface area of the nickel powder and ceramic powder was evaluated, and the number of structural defects when the unfired laminated body was pressed and cut was evaluated. The results are shown in Table 6.

From Table 6, it can be seen that the adsorption amount of one-end carboxylated ethyl cellulose to the total surface area of nickel powder and ceramic powder is particularly preferably 1.0 mg/m ² or more and 5.0 mg/m ² or less.

<<Experimental example 3>>
In Experimental Example 3, the same method as in Experimental Example 1 was used to prepare samples having different molecular weights of the cellulose derivatives contained in the conductive paste.

[Preparation of conductive paste]
45.5 parts by mass of nickel powder with a BET diameter of 177 nm (SSA = 3.8 m ² /g) and 3.0 parts by mass of ceramic powder containing barium titanate with a BET diameter of 13 nm (SSA = 77 m ² /g) as a main component. Parts by mass, 0.70 parts by mass of a polycarboxylic acid-based polymer dispersant, and 1.0 parts by mass of one-end carboxylated ethyl cellulose having a number average molecular weight shown in the "first binder" column of Table 7 as a first binder. 1 part by mass and 39.7 parts by mass of dihydroterpineol acetate were mixed and subjected to roll dispersion treatment to obtain an intermediate conductive paste.

After that, 1.1 parts by mass of the above-described copolymer C as a second binder and 8.9 parts by mass of dihydroterpineol acetate were added to the intermediate conductive paste, and dispersed using a three-roll mill. , conductive pastes according to Examples 3-1 to 3-3 shown in Table 7 were obtained.

[Evaluation of Binder Adsorption Amount and Structural Defect Occurrence]
In the same manner as in Experimental Example 1, the amount of adsorbed binder with respect to the total surface area of the nickel powder and ceramic powder was evaluated, and the number of structural defects when the unfired laminated body was pressed and cut was evaluated. The results are shown in Table 7. Table 7 also shows the evaluation results of Examples 1-10 produced in Experimental Example 1.

From Table 7, even if the molecular weight of the one-end carboxylated ethyl cellulose to be adsorbed to the nickel particles and ceramic particles was changed, there was no significant change in the adsorption amount, and no structural defects were confirmed. From this, it can be seen that there is no particular restriction on the molecular weight of the one-end carboxylated ethyl cellulose in order to obtain the effects of the present invention.

The reason why the adsorbed amount did not change significantly even when the molecular weight was changed is that the shorter the molecular chain of the one-end carboxylated ethyl cellulose, the smaller the repulsion between the molecular chains adsorbed on the surfaces of the nickel particles and the ceramic particles. , while the number of adsorbed single-end carboxylated ethyl cellulose increased, the longer the molecular chain of the single-end carboxylated ethyl cellulose, the greater the repulsion between the molecular chains adsorbed on the surfaces of the nickel particles and the ceramic particles, resulting in single-end carboxylation. It is presumed that there is a balance relationship such that the number of adsorbed ethyl cellulose decreases.

<<Experimental example 4>>
In Experimental Example 4, the same method as in Experimental Example 1 was used to prepare samples with different types of inorganic particles contained in the paste.

[Preparation of conductive paste]
45.5 parts by mass of decanoic acid-coated Cu powder with a BET diameter of 204 nm (SSA = 3.4 m ² /g) and a ceramic powder containing barium titanate with a BET diameter of 13 nm (SSA = 77 m ² /g) as a main component. 3.0 parts by mass, 0.35 parts by mass of a polycarboxylic acid polymer dispersant, and 0.8 parts by mass of one-end carboxylated ethyl cellulose having a number average molecular weight of 2.0×10 ⁴ as a first binder. , and 40.05 parts by mass of dihydroterpineol acetate were mixed and subjected to roll dispersion treatment to obtain an intermediate conductive paste.

After that, 1.4 parts by mass of the above-mentioned copolymer C as a second binder and 8.9 parts by mass of dihydroterpineol acetate were added to the intermediate conductive paste, and dispersed by a three-roll mill. , a conductive paste according to Example 4-1 shown in Table 8 was obtained.

[Preparation of ceramic paste]
33.6 parts by mass of a powder mainly composed of barium titanate having a BET diameter of 149 nm (SSA = 6.7 m ² /g), 0.45 parts by mass of a polycarboxylic acid polymer dispersant, and a first binder 0.4 parts by mass of one-end carboxylated ethyl cellulose having a number average molecular weight of 2.0 × 10 ⁴ and 40.05 parts by mass of dihydroterpineol acetate are mixed and subjected to roll dispersion treatment to obtain an intermediate ceramic paste. Obtained.

After that, 3.0 parts by mass of the above-described copolymer C as a second binder and 22.5 parts by mass of dihydroterpineol acetate were added to the intermediate ceramic paste, and dispersed using a three-roll mill. A ceramic paste according to Example 4-2 shown in Table 8 was obtained.

[Preparation of unfired laminate chip]
For the conductive paste according to Example 4-1, an unfired laminate chip was obtained in the same manner as in Experimental Example 1.

For the ceramic paste according to Example 4-2, an unfired laminate chip was obtained by the method shown below.

A ceramic material mainly composed of barium titanate with a BET diameter of 150 nm, a polyvinyl butyral resin, a solvent of toluene and echinene in a ratio of 5:5, and a plasticizer, triethylene glycol di(2-ethylhexanoate). , were mixed at a predetermined ratio and subjected to wet dispersion treatment using a bead mill to obtain a ceramic slurry.

Next, this ceramic slurry was formed on a PET (polyethylene terephthalate) film using a doctor blade method so as to have a thickness of 1.0 μm after drying to obtain a ceramic green sheet.

Next, on the ceramic green sheet, a pattern was formed so that the chip-shaped laminated body to be obtained later after cutting and firing had a planar dimension of 1.0 mm × 0.5 mm, and the nickel thickness after drying was 0.30 µm. (XRF measurement) and the average physical thickness is 0.60 μm (FIB processing cross-sectional SEM observation), the conductive paste according to Example 1-10 described above is printed by a screen printer, and the conductive paste to be the internal electrode is printed. A flexible paste coating was formed.

After that, the ceramic paste according to Example 4-2 shown in Table 8 was applied to the place where the conductive paste coating film was not formed by a screen printing machine so that the average physical thickness was 0.30 μm (FIB processed cross-sectional SEM observation). and formed a coating film for compensating for a step due to the thickness of the conductive paste coating film to be the internal electrode.

Next, after peeling each ceramic green sheet from the PET film, first, 50 ceramic green sheets not printed with a conductive paste coating were stacked, and then 350 sheets printed with a conductive paste coating. The laminated structure obtained by stacking the ceramic green sheets and further stacking 30 ceramic green sheets on which the conductive paste coating film was not printed was placed in a predetermined mold. Then, the laminate structure in the mold was pressed to obtain an unfired laminate. The obtained unfired laminate was heated to 90° C. and cut into a predetermined size by press-cutting to obtain an unfired laminate chip according to Example 4-2.

[Evaluation of Occurrence of Structural Defects]
For Example 4-1, the same method as in Example 1 was used to evaluate the amount of binder adsorption with respect to the total surface area of the nickel powder and ceramic powder, and to evaluate the number of structural defects when the unfired laminate was cut. bottom.

On the other hand, in Example 4-2, for each of 100 unfired laminate chips randomly selected from the above-described unfired laminate chips, the cut surface of the press cutting was observed with an optical microscope, and structural defects were identified. The presence or absence of cohesive failure (peeling within the internal electrode layer or within the step compensation coating) in the conductive paste coating or in the step compensation coating was confirmed.

The column "number of structural defects" in Table 8 shows the number of laminate chips in which structural defects were observed among 100 laminate chips. Also, the "determination" in Table 8 follows the same criteria as the "determination" in Tables 3 and 4.

Looking at Table 8, it can be seen that if the binder was able to confirm the adsorption effect in combination with nickel particles, it could be combined with ceramic particles such as _BaTiO3 particles even in combination with other metal particles such as copper particles. It can be seen that a similar effect can be obtained even in combination. Therefore, the inorganic particles contained in the electronic component paste may be any inorganic particles as long as they can adsorb a cellulose derivative having a one-end carboxyl group or a one-end carboxylate. I understand.

1 inorganic particles 2 comb-shaped polymer dispersant 3 low-molecular-weight dispersant 4 second binder 5 first binder

Claims (12)

including inorganic particles, a dispersant, a binder and an organic solvent,
The binder includes a first binder adsorbed on the surfaces of the inorganic particles and a second binder not adsorbed on the surfaces of the inorganic particles,
At least the first binder is a cellulose derivative having one terminal carboxyl group or one terminal carboxylate,
Paste for electronic parts. The paste for electronic parts according to claim 1, wherein the second binder is a cellulose derivative having one terminal carboxyl group or one terminal carboxylate. The electronic component paste according to claim 1, wherein the second binder is a cellulose derivative that does not have a one-end carboxyl group or a one-end carboxylate. The electronic component paste according to claim 1, wherein the second binder is a copolymer having a cellulose derivative portion or a mixture of multiple polymers containing a cellulose derivative. The cellulose derivative having one terminal carboxyl group or one terminal carboxylate as the first binder is 1.0 mg/m ² or more and 5.0 mg/m ² or less with respect to the total surface area of the inorganic particles. The electronic component paste according to any one of claims 1 to 4. The electronic component paste according to any one of claims 1 to 5, wherein the inorganic particles include at least one of ceramic particles and metal particles. The electronic component paste according to claim 6, wherein the ceramic particles contain at least one element selected from Ba, Ti, Ca, Zr and Sr. 7. The electronic component paste according to claim 6, wherein said metal particles contain at least one metal selected from Cu, Ni, Au and Ag. The electronic component paste according to any one of claims 1 to 8, wherein the cellulose derivative having one terminal carboxyl group or one terminal carboxylate is a cellulose ether having one terminal carboxyl group or one terminal carboxylate. 10. The cellulose ether according to claim 9, wherein the cellulose ether having one terminal carboxyl group or one terminal carboxylate is at least one selected from methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylhydroxyethylcellulose and hydroxypropylmethylcellulose. Paste for electronic parts. The electronic component paste according to any one of claims 1 to 10, wherein the dispersant is a polymer dispersant. The electronic component paste according to claim 11, wherein the polymer dispersant is a polycarboxylic acid-based dispersant.

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