WO2025150393A1 - Vehicle, conductive paste, electronic component, and multilayer ceramic capacitor - Google Patents

Abstract

To provide a vehicle and a conductive paste with which it is possible to suppress sheet attack of a green sheet while maintaining good smoothness and dry film density of a conductive paste that uses a fine conductive powder and a ceramic powder for miniaturization and thinning of a multilayer ceramic electronic component, and to provide an electronic component and a multilayer ceramic capacitor.　Provided is a vehicle containing a binder resin and an organic solvent, wherein the binder resin contains a polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded by a sulfur atom, the molar ratio of sulfur atoms contained in the polymer compound to the cellulose compound is 0.3-1.7, and the hydrogen bonding term δh of the Hansen solubility parameter of the organic solvent is 6.5 MPa0.5 or less.

Description

Vehicle, conductive paste, electronic component, and multilayer ceramic capacitor

The present invention relates to a vehicle, a conductive paste, an electronic component, and a multilayer ceramic capacitor.

As electronic devices such as mobile phones and digital devices become smaller and more powerful, there is a demand for electronic components, including multilayer ceramic capacitors, to be smaller and have higher capacity. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by thinning these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacity.

For example, a multilayer ceramic capacitor is manufactured as follows. First, a conductive paste for internal electrodes is printed (applied) in a predetermined electrode pattern on the surface of a green sheet containing a dielectric powder such as barium titanate (BaTiO ₃ ) and a binder resin such as polyvinyl acetal resin (PVA), and then dried to form a dry film. Next, the dry film and the green sheet are alternately stacked and heated and pressed to form a laminate in which the dry film and the green sheet are integrated. This laminate is cut, and an organic binder removal treatment is performed in an oxidizing atmosphere or an inert atmosphere, and then sintered to obtain a sintered chip. Next, a paste for external electrodes is applied to both ends of the sintered chip, and the chip is sintered to form external electrodes, and then nickel plating or the like is applied to the surface of the external electrodes to obtain a multilayer ceramic capacitor (MLCC). The conductive paste for internal electrodes contains a conductive powder such as nickel powder, a ceramic powder such as barium titanate powder, an organic binder, and a solvent.

In recent years, there has been a demand for MLCCs to be even smaller and have larger capacities. For example, for internal electrodes using nickel and other materials, efforts are being made to make the electrode film thinner, with greater density and continuity, and for ceramic dielectric materials and dielectric layers using these, efforts are being made to increase the dielectric constant and make the film thinner, with dielectric layers with thicknesses of 1.0 μm or less already in practical use. It is also desirable to make the electrode film 1.0 μm or less in thickness.

When MLCCs are made thinner, the adhesion between the green sheets and the internal electrode layers decreases, causing problems such as frequent curling and lamination misalignment due to poor adhesion during lamination. In multilayer ceramic capacitors, for example, this poor adhesion can cause short circuits. In particular, the need for multilayer MLCCs requires that the thickness of each dielectric layer be thinned by using fine-grained dielectric powder and that the number of layers be increased, so improving this poor adhesion is desirable. If the adhesion between sheets is weak, sintering can cause structural defects such as voids, delamination, and cracks, reducing the yield of MLCCs. In other words, the purpose of improving the adhesion between the internal electrode layers and the green sheets is to prevent cracking.

If polyvinyl acetal resin is used as the organic binder in the conductive paste, it is possible to prevent the electrodes from peeling off when the laminate is cut. It is also desirable to add cellulose resin to the conductive paste to give it the desired rheological properties.

Patent Document 1 therefore discloses that the internal electrode paste can contain an organic resin, and that the organic binder resin is preferably a mixture of ethyl cellulose (EC) and polyvinyl butyral (PVB) resin, which is a type of polyvinyl acetal (PVA) resin.

However, if the conductive paste for the internal electrodes contains PVA, the solvent used for the conductive paste must dissolve PVA. In that case, depending on the solvent that dissolves the PVA contained in the conductive paste, the PVA contained in the green sheet may be dissolved and eroded, resulting in sheet attack. If sheet attack occurs, the thickness of the green sheet may become locally thin or holes may appear in the green sheet, resulting in poor formation of the internal electrodes or the green sheet between the internal electrodes may disappear, connecting the internal electrodes and causing a short circuit. Therefore, Patent Document 2 discloses a special solvent composition that can deal with sheet attack.

Patent Publication 2009-147359 Patent Publication No. 2020-057691

Generally, when two organic binder resins with significantly different structures are mixed together, the result is almost always an incompatible combination. In the case of an incompatible system, the two organic binder resins are essentially not mixed together and exist independently, so not only do they fail to provide the performance expected from the use of the two organic binder resins, but they often have significantly reduced functionality compared to when each organic binder is used alone. Furthermore, because the mixture contains a solvent suitable for the two organic binder resins, there is a high risk that the solvent that dissolves PVA will cause the above-mentioned sheet attack.

If organic binder resins that do not normally mix can be made to be compatible with each other, it will be possible to stabilize the interface between the different polymers and achieve a uniform and stable dispersion state, combining the characteristics of both.

The conductive paste disclosed in Patent Document 1 contains polyvinyl butyral resin, which improves the adhesion between the dried film and the green sheet. However, this technology uses ethyl cellulose resin and polyvinyl butyral resin in combination, which results in poor compatibility between the two resins, and can result in insufficient dispersion of the conductive powder and ceramic powder in the conductive paste, or in insufficient density and smoothness of the dried film of the conductive paste.

In addition, when the conductive paste contains polyvinyl acetal resin and cellulose-based resin, it is important to select a solvent that can dissolve both resins or a mixture of multiple types of solvents as the solvent used for the conductive paste. At the same time, it is necessary to select a solvent that can suppress sheet attack. In particular, when selecting a solvent for the conductive paste that can dissolve polyvinyl acetal resin, sheet attack may occur if the solubility of that solvent in the polyvinyl acetal resin contained in the green sheet is not taken into consideration.

In light of these circumstances, the present invention aims to provide a vehicle, conductive paste, electronic component, and multilayer ceramic capacitor that can suppress sheet attack on green sheets while maintaining good smoothness and density of the dried film of the conductive paste in a conductive paste that uses fine conductive powder or ceramic powder to make multilayer ceramic electronic components smaller and thinner.

In order to solve the above problems, the vehicle of the present invention is a vehicle containing a binder resin and an organic solvent, wherein the binder resin contains a polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded together via sulfur atoms, the molar ratio of sulfur atoms contained in the polymer compound to the cellulose-based compound is 0.3 to 1.7, and the hydrogen bond term δh of the Hansen solubility parameter of the organic solvent is 6.5 MPa ^0.5 or less.

The polymer compound may have a hydrogen bond term δh of Hansen solubility parameters of 6.5 to 8.5 MPa ^0.5 .

The cellulose compound may be a cellulose derivative having a thiol group or a vinyl group, the polyvinyl acetal compound may be a polyvinyl acetal resin having a thiol group or a vinyl group, and if the cellulose derivative has a thiol group, the polyvinyl acetal resin may have a vinyl group that reacts with the thiol group, and if the cellulose derivative has a vinyl group, the polyvinyl acetal resin may have a thiol group that reacts with the vinyl group.

The cellulose derivative may be ethyl cellulose having a thiol group or a vinyl group, and the polyvinyl acetal resin may be polyvinyl butyral having a thiol group or a vinyl group.

The cellulose-based compound may be a first esterification reaction product formed by dehydration condensation of a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of cellulose, and the polyvinyl acetal-based compound may be a second esterification reaction product formed by dehydration condensation of a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of polyvinyl acetal. When the first esterification reaction product has a thiol group, the second esterification reaction product has a vinyl group, and when the first esterification reaction product has a vinyl group, the second esterification reaction product has a thiol group. The polymer compound may be a thiol-ene reaction product of the first esterification reaction product and the second esterification reaction product.

The first esterification reaction product may be an esterification reaction product obtained by dehydration condensation of the carboxy group of 3-allyloxypropionic acid and the hydroxyl group of ethyl cellulose, and the second esterification reaction product may be an esterification reaction product obtained by dehydration condensation of the carboxy group of 3-mercaptopropionic acid and the hydroxyl group of polyvinyl butyral.

In order to solve the above problems, the conductive paste of the present invention is a conductive paste containing the vehicle of the present invention, a conductive powder, and a ceramic powder, and the hydrogen bond term δh of the Hansen solubility parameter of the organic solvent in the conductive paste is 6.5 MPa ^0.5 or less.

The number average particle size of the conductive powder may be 0.05 μm or more and 1.0 μm or less.

The ceramic powder may include barium titanate.

The number average particle size of the ceramic powder may be 0.01 μm or more and 0.5 μm or less.

The content of the ceramic powder may be 1% by mass or more and 20% by mass or less.

The conductive paste of the present invention may be used for internal electrodes of multilayer ceramic components.

In order to solve the above problems, the electronic component of the present invention is an electronic component formed using the conductive paste of the present invention.

In order to solve the above problems, the multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor that has at least a laminate in which a dielectric layer and an internal electrode layer are laminated, and the internal electrode layer is formed using the conductive paste of the present invention.

The vehicle of the present invention has the characteristics of polyvinyl acetal resin by selecting the binder resin, while the sheet attack of the conductive paste can be suppressed by selecting the solvent. Furthermore, the conductive paste using the vehicle of the present invention has excellent dispersibility of the conductive powder, and the dried film after application has high surface smoothness. Furthermore, the electrode pattern of electronic components such as multilayer ceramic capacitors formed using the conductive paste of the present invention has small surface roughness and high dried film density.

FIG. 1A is a perspective view showing a multilayer ceramic capacitor according to this embodiment. FIG. 1B is a cross-sectional view showing the multilayer ceramic capacitor according to this embodiment.

The following describes one embodiment of the vehicle, conductive paste, electronic component, and multilayer ceramic capacitor of the present invention.

[Vehicle]
The vehicle of the present invention contains a binder resin and an organic solvent, which will be described below.

<Binder resin>
The binder resin contained in the vehicle contains a polymeric compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded together via sulfur atoms, and the molar ratio of sulfur atoms contained in the polymeric compound to the cellulose-based compound is 0.3 to 1.7, i.e., in the polymeric compound, the ratio of cellulose-based compound:sulfur atom is 1.0:0.3 to 1.7.

The mass average molecular weight (Mw) of the polymer compound is preferably 20,000 to 200,000, as a standard polystyrene equivalent value by gel permeation chromatography (GPC). If the number average molecular weight of the polymer compound is less than 20,000, the viscosity of the conductive paste made using it will be extremely low, and it may be difficult to adjust the viscosity to an appropriate level for the conductive paste. If the mass average molecular weight of the polymer compound exceeds 200,000, the viscosity of the conductive paste made using it will be extremely high, and it may be difficult to adjust the viscosity to an appropriate level for the conductive paste, or it may be necessary to reduce the content of the conductive powder or ceramic powder below the appropriate level in order to adjust the viscosity to an appropriate level.

The molecules of the polymer compound of this embodiment contain a portion due to a cellulose-based compound and a portion due to a polyvinyl acetal-based compound, so that the dried film obtained from the conductive paste of this embodiment can have the surface smoothness due to the cellulose-based compound and the adhesion to the green sheet due to the polyvinyl acetal-based compound. Furthermore, by having the structures of a cellulose-based compound and a polyvinyl acetal-based compound, which are incompatible with each other, in the same molecule, the polymer compound can also eliminate poor dispersion of the conductive paste.

Here, if the molar ratio of the sulfur atoms contained in the polymer compound to the cellulose-based compound is 0.5 to 2, the surface roughness of the dried film is superior to that of a conventional conductive paste that uses cellulose and polyvinyl acetal resin in combination as a binder resin. Furthermore, if the molar ratio is 0.3 to 1.7, the surface roughness and dry film density of the dried film of the conductive paste are superior. The molar ratio of the sulfur atoms contained in the polymer compound to the cellulose-based compound is 0.3 to 1.7, and more preferably, the molar ratio is 0.5 to 1.5.

(Hydrogen bond term δh of Hansen solubility parameter of polymer compound)
Hansen solubility parameters are known as a measure of the solubility of resins in solvents. Hansen solubility parameters (HSP) are based on the idea that two substances with similar intermolecular interactions are easily dissolved in each other. The idea of Hansen solubility parameters also applies between resins and solvents. Hansen solubility parameters have three terms: a dispersion term (δd), a polar term (δp), and a hydrogen bond term (δh). In the vehicle and conductive paste of this embodiment, the hydrogen bond term (δh) affects the dissolution of cellulose, polyvinyl acetal resin, and the polymer compound in organic solvents.

Hansen solubility parameters may vary depending on the source, but in this embodiment, for solvents registered in the database of the Hansen solubility parameter software HSPiP (Hansen Solubility Parameter in Practice) version 5, the registered values were used. For solvents not registered, the estimated values calculated by HSPiP version 5 were used. For resins registered in the database, the registered values were used. For resins not registered in the database, tests were conducted to dissolve the resin in 20 types of solvents with known HSP values, and the Hansen ball was searched for and calculated using HSPiP version 5 from the HSP values of soluble solvents.

The δh of the HSP of ethyl cellulose, which is a cellulose-based resin, is 5.5 to 6.5 MPa ^0.5 , and the δh of the HSP of polyvinyl butyral resin, which is a polyvinyl acetal resin, is 10 to 11 MPa ^0.5 . The polymer compound contained in the vehicle and conductive paste of this embodiment has a structure derived from polyvinyl acetal resin in its molecule, but its δh of HSP is 6.5 to 8.5 MPa ^0.5 , which is close to that of ethyl cellulose.

Here, the value of each term of the HSP of each resin or polymer compound is the value corresponding to the center of the Hansen sphere. This means that the polymer compound of this embodiment can use a solvent suitable for dissolving ethyl cellulose. Therefore, it is possible to reduce the amount of solvent used that is likely to cause sheet attack and is suitable for dissolving the polyvinyl acetal resin contained in the green sheet. The solubility of the polymer compound of this embodiment in solvents makes it possible to suppress sheet attack. The polymer compound of this embodiment has a cellulose structure in its molecule, and therefore dissolves in a solvent suitable for cellulose.

(polymer compound)
The polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded, which can be used in the present embodiment, will be described in more detail.

Both cellulose and polyvinyl acetal have hydroxyl groups in their molecules. A functional group capable of reacting with other compounds to form bonds is introduced to the hydroxyl groups of cellulose, and a cellulose-based compound chemically modified with a reactive functional group is prepared. On the other hand, a functional group capable of reacting with other compounds to form bonds and different from the functional group introduced to the cellulose-based compound is introduced to the hydroxyl groups of the polyvinyl acetal-based polymer compound, and a polyvinyl acetal-based compound chemically modified with a reactive functional group is prepared. In other words, the reactive functional group introduced to the cellulose-based compound and the reactive functional group introduced to the polyvinyl acetal-based compound are different. Note that the functional group introduced to the cellulose-based compound and the functional group introduced to the polyvinyl acetal-based compound react, but the same functional group does not react easily. The reason why the same functional group does not react easily is to prevent cellulose-based compounds and polyvinyl acetal-based compounds from bonding with each other.

Then, if the functional group introduced into the cellulose compound and the functional group introduced into the polyvinyl acetal compound are bonded, a polymer compound in which the cellulose compound and the polyvinyl acetal compound are bonded can be obtained. Specifically, if a thiol group is introduced into cellulose to make a cellulose compound, and a vinyl group is introduced into a polyvinyl acetal resin to make a polyvinyl acetal compound, the thiol group and the vinyl group are bonded to the double bond of the vinyl group and the sulfur atom of the thiol group in the presence of a nucleophile or under conditions that generate radicals. As the polymer compound of the binder resin used in the conductive paste of this embodiment, a polymer compound in which the cellulose compound and the polyvinyl acetal compound are bonded can be obtained by utilizing the bonding reaction between the thiol group and the vinyl group. Of course, a vinyl group can be introduced into the hydroxyl group of cellulose to make a cellulose compound, and a thiol group can be introduced into the hydroxyl group of the polyvinyl acetal resin to make a polyvinyl acetal compound.

In other words, the cellulose compound may be a cellulose derivative having a thiol group or a vinyl group, and the polyvinyl acetal compound may be a polyvinyl acetal resin having a thiol group or a vinyl group. When the cellulose derivative has a thiol group, the polyvinyl acetal resin has a vinyl group that reacts with the thiol group, and when the cellulose derivative has a vinyl group, the polyvinyl acetal resin has a thiol group that reacts with the vinyl group.

The cellulose-based polymer compound used as the binder resin of the conductive paste of this embodiment is preferably a polymer compound that has been chemically modified by bonding with the hydroxyl groups of cellulose, a natural polymer. Note that the chemical modification here is different from the chemical modification that introduces functional groups with the above-mentioned reactivity, and is a chemical modification for the purposes of alkyl etherification, esterification, etc., described below.

The bonding of compounds with the hydroxyl groups of cellulose can be by alkyl etherification, esterification, etc. Examples of celluloses with hydroxyl groups include methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, cellulose acetate (acetyl cellulose, diacetyl cellulose, triacetyl cellulose, etc.), cellulose acetate propionate, cellulose acetate butyrate, nitrocellulose, etc. Only one type of cellulose can be used, or two or more types can be used in combination.

Since the conductive paste of the embodiment contains an organic solvent, it is preferable that the cellulose also dissolves in the organic solvent. From the standpoint of solubility in organic solvents and the smoothness of the dried film of the conductive paste, it is more preferable to use ethyl cellulose as the cellulose.

The molecular weight of the cellulose affects the viscosity of the conductive paste of this embodiment. The number average molecular weight (Mn) of the cellulose, calculated as a standard polystyrene equivalent by GPC, is preferably 10,000 to 100,000, and more preferably 10,000 to 80,000.

If the number average molecular weight of cellulose is less than 10,000, the viscosity of the conductive paste produced using it may be lower than the appropriate viscosity, and if the number average molecular weight of cellulose exceeds 100,000, the viscosity of the conductive paste produced using it may be too high.

Not all of the hydroxyl groups in cellulose are chemically modified. In the case of cellulose before chemical modification, the glucose rings that make up the cellulose have three hydroxyl groups per ring structure, but in the case of cellulose after chemical modification, on average 0.1 to 1 hydroxyl group per ring structure of the glucose rings that make up the cellulose remains as a hydroxyl group and is not chemically modified. In this invention, reactive functional groups are introduced into these unmodified hydroxyl groups.

On the other hand, polyvinyl acetal is usually a polymer composed of vinyl acetal/vinyl alcohol/vinyl acetate monomer units, and can be obtained by saponifying polyvinyl acetate to polyvinyl alcohol, which is then acetalized. Specifically, examples of polyvinyl acetal include polyvinyl alcohol that has been butyralized (polyvinyl butyral) and polyvinyl alcohol that has been formalized (polyvinyl formal).

Polyvinyl acetal may be a commercially available product, and various polyvinyl acetals with different degrees of butyralization, degrees of formalization, amounts of acetyl groups, amounts of hydroxyl groups, molecular weights, etc. are sold by Sekisui Chemical Co., Ltd., Kuraray Co., Ltd., etc. Only one type of polyvinyl acetal may be used, or two or more types may be used in combination.

The polyvinyl acetal is preferably one that is soluble in an organic solvent. Due to its high solubility in organic solvents, the polyvinyl acetal is more preferably polyvinyl butyral.

The molecular weight of the polyvinyl acetal used as the polymer compound affects the film strength and solution viscosity. Therefore, the number average molecular weight of the polyvinyl acetal, calculated as a standard polystyrene equivalent value by GPC, is preferably in the range of 5,000 to 150,000, and more preferably in the range of 10,000 to 100,000.

If the number average molecular weight of polyvinyl acetal is less than 5,000, the viscosity of the conductive paste produced using it may be lower than the appropriate viscosity, and if the number average molecular weight of polyvinyl acetal is more than 150,000, the viscosity of the conductive paste produced using it may be too high.

Polyvinyl acetal has at least one hydroxyl group per molecule. Generally, polyvinyl acetal has 20-40 mol% of hydroxyl groups as vinyl alcohol units that make up the polymer. These hydroxyl groups are chemically modified by introducing reactive functional groups.

As a compound that reacts with the hydroxyl groups of cellulose or polyvinyl acetal to chemically modify it, a compound that has a thiol group or vinyl group at one end and a carboxyl group at the other end can be used. The carboxyl group of the compound undergoes dehydration condensation with the hydroxyl groups of the cellulose-based polymer compound or polyvinyl acetal compound to form an ester bond.

(Method of synthesizing polymer compounds)
An example of a method for synthesizing the polymer compound used in this embodiment will be described below. To obtain a cellulose-based compound or a polyvinyl acetal-based compound, a compound having a functional group reactive with a hydroxyl group and a functional group reactive with other compounds may be esterified or etherified with the hydroxyl group of cellulose or the hydroxyl group of polyvinyl acetal. Examples of the functional group reactive with a hydroxyl group include a carboxyl group and a hydroxyl group.

The esterification reaction can be carried out, for example, using a condensing agent. Examples of condensing agents include carbodiimide, diphenylphosphoryl azide, and 1-hydroxybenzotriazole. The condensing agents may be used alone or in combination of two or more. Among them, carbodiimide is preferred because it has excellent versatility and reactivity, and can proceed at low temperatures and without being affected by moisture in the reaction environment.

Carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide, and N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide methiodide. Among them, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferred from the viewpoint of availability. When using carbodiimide, it is also preferable to use a base such as dimethylaminopyridine or triethylamine as a reaction accelerator in the range of 0.01 mol % to 10 mol % relative to the carbodiimide.

On the other hand, the etherification reaction can be carried out efficiently by using alkali metal hydroxides such as KOH and NaOH, or alkali metal hydrides such as NaH and KH as reaction catalysts.

To obtain a cellulose-based compound, cellulose is dissolved in an aprotic solvent such as ethyl acetate, mixed with a compound having a carboxyl group that forms an ester bond with a hydroxyl group and a vinyl or thiol group that is a functional group that reacts with other compounds, and it is also preferable to use a condensing agent and a base such as dimethylaminopyridine as a nucleophile to promote the esterification reaction in the range of 0.01 mol% to 10 mol%.

The polymer compound used in this embodiment has a molar ratio of sulfur atoms to the cellulose compound of 0.3 to 1.7 (cellulose compound:sulfur atoms = 1.0:0.3 to 1.7). Therefore, for 1 mol of cellulose, 0.3 to 1.7 mol of a compound with a functional group that reacts with other compounds must be added.

The reaction temperature for synthesizing cellulose compounds is preferably in the range of room temperature to 50°C. In the system in which the synthesis reaction of cellulose compounds is completed, unreacted cellulose without functional groups having reactivity with other compounds, cellulose compounds with one functional group having reactivity with other compounds, and cellulose compounds with multiple functional groups having reactivity with other compounds are mixed. Chemical modification is a matter of probability, but the majority of cellulose compounds have one hydroxyl group of cellulose chemically modified. In the present invention, the mixture of unreacted cellulose, cellulose with multiple functional groups, and cellulose with one functional group is called the cellulose compound. Then, when the synthesis of the cellulose compound is completed, the solvent can be removed by distillation.

To synthesize polyvinyl acetal compounds, it is preferable to dissolve polyvinyl acetal in an aprotic solvent such as ethyl acetate, mix with a compound that has a carboxyl group that forms an ester bond with a hydroxyl group and a vinyl or thiol group that is a functional group that reacts with other compounds, and use a condensing agent and a base such as dimethylaminopyridine as a nucleophile to promote the esterification reaction in the range of 0.01 mol% to 10 mol%.

The reaction temperature for chemically modifying the hydroxyl groups of polyvinyl acetal is preferably in the range of room temperature to 50°C. Although a functional group such as a thiol group or a vinyl group is introduced into the polyvinyl acetal, the functional group is not introduced into all of the polyvinyl acetal, and unreacted polyvinyl acetal is mixed in. In the present invention, the mixture of these unreacted polyvinyl acetals and polyvinyl acetals with functional groups introduced therein is called a polyvinyl acetal-based compound. Then, once the synthesis of the polyvinyl acetal-based compound is completed, the solvent can be removed by distillation.

The polymer compound used in this embodiment is synthesized by dissolving a cellulose-based compound and a polyvinyl acetal-based compound in a solvent, adding a radical generator, and heating the mixture, causing a reaction between the vinyl group in either the cellulose-based compound or the polyvinyl acetal-based compound and the thiol group in the other compound, resulting in the cellulose-based compound and the polyvinyl acetal-based compound bonding together.

Alternatively, the cellulose compound and the polyvinyl acetal compound may be dissolved in a solvent, and a nucleophilic agent such as an amine or other base may be added and heated.

The temperature for the reaction to bond the cellulose compound and the polyvinyl acetal compound can be selected appropriately, but a temperature of 60°C or higher is preferable.

For example, the cellulose derivative may be ethyl cellulose having a thiol group or a vinyl group, and the polyvinyl acetal resin may be polyvinyl butyral having a thiol group or a vinyl group.

Specifically, the cellulose-based compound may be a first esterification reaction product in which a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of cellulose undergo dehydration condensation, and the polyvinyl acetal-based compound may be a second esterification reaction product in which a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of polyvinyl acetal undergo dehydration condensation. When the first esterification reaction product has a thiol group, the second esterification reaction product has a vinyl group, and when the first esterification reaction product has a vinyl group, the second esterification reaction product has a thiol group, and the polymer compound may be a thiol-ene reaction product of the first esterification reaction product and the second esterification reaction product.

More specifically, the first esterification reaction product may be an esterification reaction product in which the carboxy group of 3-allyloxypropionic acid and the hydroxyl group of ethyl cellulose are dehydrated and condensed, and the second esterification reaction product may be an esterification reaction product in which the carboxy group of 3-mercaptopropionic acid and the hydroxyl group of polyvinyl butyral are dehydrated and condensed.

The reaction to bond the cellulose compound and the polyvinyl acetal compound is desirably carried out in a solvent for the vehicle of this embodiment, which will be described later. When the reaction to bond the cellulose compound and the polyvinyl acetal compound is carried out in a solvent for the vehicle, the polymer compound of this embodiment is obtained in a state dissolved in the solvent for the vehicle. In other words, by carrying out the reaction to bond the cellulose compound and the polyvinyl acetal compound, a vehicle in which the polymer compound is dissolved in the solvent can be obtained.

Furthermore, the vehicle of this embodiment may contain a cellulose resin and a polyvinyl acetal resin in addition to the polymer compound, or may contain either a cellulose resin or a polyvinyl acetal resin, or both, in addition to the polymer compound.

Generally, cellulose resin and polyvinyl acetal resin are not compatible as described above. However, the polymer compound can help the cellulose resin and polyvinyl acetal resin to be compatible with each other, and can suppress phase separation between the cellulose resin and the polyvinyl acetal resin. In addition, since the polymer compound can help the cellulose resin and the polyvinyl acetal resin to be compatible with each other, even if a solvent that dissolves cellulose resin more easily than polyvinyl acetal resin is used as a vehicle or conductive paste, the polymer compound coexists with the polyvinyl acetal resin, thereby showing the effect of dissolving the polyvinyl acetal resin. These effects are due to the fact that the molecules of the polymer compound have a cellulose compound skeleton and a polyacetal compound skeleton.

In the vehicle of this embodiment, the ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound in the binder resin is 20% by mass or more, and preferably 30% by mass or more. If the ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound is less than 20% by mass, the suppression of phase separation will only occur in a portion of the conductive paste, and satisfactory results may not be obtained. The ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound in the binder resin can be 99% by mass or less, or 95% by mass or less.

When such phase separation occurs, the binder resin, conductive powder, and ceramic powder are unevenly distributed in the dried film obtained by printing (spraying) the conductive paste and drying it, and the internal electrode obtained by firing the dried film may have voids where no conductive material is present due to the uneven distribution of the binder resin and ceramic powder. When such voids occur in the internal electrode, the area of the internal electrode becomes narrow, leading to a decrease in the capacity of the MLCC. The effect of the polymer compound in suppressing phase separation between the cellulose resin and the polyvinyl acetal resin contributes to uniform particle distribution in the dried film. As a result, the film breakage phenomenon of the electrode layer after firing is resolved, and the capacity of the MLCC increases.

The vehicle of this embodiment can contain one or more resins selected from cellulose resin and polyvinyl acetal resin, which improves the freedom to adjust the viscosity of the conductive paste. In other words, since cellulose resin and polyvinyl acetal resin can be added appropriately within the range of this embodiment, it becomes easier to adjust the viscosity of the conductive paste.

As the cellulose resin that can be used, methyl cellulose resin, ethyl cellulose resin, ethyl hydroxyethyl cellulose resin, nitrocellulose resin, etc. can be selected, and ethyl cellulose resin is preferable. Furthermore, these cellulose resins can be used alone, or two or more types can be used in combination. Furthermore, as the polyvinyl acetal resin that can be used, polyvinyl butyral can be selected. Only one of the cellulose resin and the polyvinyl acetal resin can be used, or both can be used. Furthermore, the blending ratio of the cellulose resin, the polyvinyl acetal resin, and the polymer compound can be appropriately selected as long as it does not deviate from the scope of this embodiment. By selecting these resins and the blending ratio of the resins, the viscosity of the conductive paste and the adhesion of the resulting dried film to the green sheet can be appropriately adjusted.

In this embodiment, in addition to cellulose resin and polyvinyl acetal resin, it is also possible to add known binder resins such as acrylic resin and maleic acid ester resin. The number average molecular weight of resins that can be added in this way, in addition to cellulose resin and polyvinyl acetal resin, is about 20,000 to 300,000 as determined by GPC (gel permeation chromatography) analysis.

<Organic Solvent>
The solvent that can be used for the vehicle of this embodiment has an HSP δh of 6.5 MPa ^0.5 or less, preferably 6 MPa ^0.5 or less, more preferably 5.5 MPa ^0.5 or less, and even more preferably 5 MPa ^0.5 or less. On the other hand, the lower limit of the HSP δh of the solvent is 0.5 MPa ^0.5 or more, preferably 1.5 MPa ^0.5 or more, and more preferably 2.5 MPa ^0.5 or more. The solvent may be one type or a mixed solvent in which a plurality of types are mixed. The Hansen solubility parameter of the mixed solvent can be calculated by multiplying the volume fraction of the solvents constituting the mixed solvent by the δd, δp, and δh of the HSP of the solvent and adding them up. Of course, if the HSP δh of the solvent used for the vehicle of this embodiment is 6.5 MPa ^0.5 or less, it is suitable for dissolving polymer compounds and cellulose-based resins, but is not suitable for dissolving the butyral resin contained in the green sheet. The sheet attack is suppressed by taking into consideration the solubility of the butyral resin in the solvent that can be used in the vehicle of this embodiment. If the lower limit value of δh of the HSP is 0.5 MPa ^or more, it is possible to dissolve polymer compounds and cellulose-based resins.

Such solvents that can be used as a single solvent include acetate-based solvents such as isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, and diethylene glycol monoethyl ether acetate; ether-based solvents such as ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and ethylene glycol dibutyl ether; and terpene-based solvents such as dihydroterpinyl acetate and terpinyl acetate.

In addition, in a mixed solvent composed of a plurality of solvents, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, diethylene glycol monobutyl ether acetate, terpineol, and dihydroterpineol may be added, provided that the HSP δh value is 6.5 MPa ^or less.

The solvent contained in the vehicle of this embodiment has an HSP δh of 6.5 MPa ^0.5 or less, preferably 6 MPa ^0.5 or less, and more preferably 5.5 MPa ^0.5 or less. Further examples include hydrocarbon solvents such as tridecane, nonane, and cyclohexane, and petroleum-based hydrocarbon solvents such as mineral spirits. The organic solvent may be one type or a mixed solvent using two or more types.

(Contents of binder resin and organic solvent in vehicle)
The vehicle is one of the raw materials of the conductive paste described later, and may be a mixture of a polymer compound and an organic solvent obtained by reacting a cellulose compound with a polyvinyl acetal compound in an organic solvent. The vehicle may also be a mixture to which an organic solvent is further added. The vehicle may also be a vehicle obtained by dissolving a solid polymer compound in an organic solvent.

Therefore, the binder resin content and organic solvent content in the vehicle can be adjusted as appropriate. For example, the mass ratio of the binder resin to the organic solvent may be adjusted so that the entire amount of the binder resin and organic solvent in the conductive paste to be manufactured is contained in the vehicle, or the mass ratio of the binder resin to the organic solvent may be adjusted so that the entire amount of the binder resin and a portion of the organic solvent in the conductive paste are contained in the vehicle. For example, the mass ratio of the binder to the organic solvent in the vehicle may be 5-50:95-50.

[Conductive paste]
The conductive paste of the present embodiment contains a vehicle, a conductive powder, and a ceramic powder. Each component will be described in detail below.

<Conductive powder>
The conductive powder is not particularly limited, and metal powder can be used, for example, powder of one or more types selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, Ni or its alloy powder is preferred from the viewpoints of conductivity, corrosion resistance, and cost. As the Ni alloy, for example, an alloy of Ni and at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd (Ni alloy) can be used. The Ni content in the Ni alloy is, for example, 50 mass% or more, preferably 80 mass% or more. In addition, the Ni powder may contain about several hundred ppm of S in order to suppress rapid gas generation due to partial thermal decomposition of the binder resin during the binder removal process.

The method for producing the conductive powder is not particularly limited, and examples that can be used include a method in which chloride vapor is directly precipitated from the gas phase in hydrogen gas, an atomization method using molten metal, a spray pyrolysis method using an aqueous solution, and a wet method in which the raw metal salt is reduced in an aqueous solution.

The number average particle diameter of the conductive powder is not particularly limited and may be selected according to the size of the electronic components to be used, for example, 0.05 μm or more and 1.0 μm or less. For multilayer ceramic capacitors, which are becoming thinner, the number average particle diameter of the conductive powder is preferably 0.5 μm or less, and more preferably 0.3 μm or less. If the number average particle diameter exceeds 0.5 μm, the internal electrode surface becomes very uneven, which may degrade the electrical characteristics of the capacitor, and is not preferable. In addition, the lower limit of the number average particle diameter of the conductive powder is not particularly limited, but is, for example, 0.03 μm or more. If the number average particle diameter is smaller than 0.03 μm, handling may become extremely difficult.

The number average particle size of the conductive powder is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle size of each of multiple particles from an image observed with an SEM at a magnification of 10,000 times.

The content of the conductive powder is preferably 30% by mass or more and less than 70% by mass, and more preferably 40% by mass or more and less than 60% by mass, based on the total amount of the conductive paste. When the content of the conductive powder is 30% by mass or more and less than 70% by mass, based on the total amount of the conductive paste, the conductive paste has excellent conductivity and dispersibility.

<Ceramic powder>
The ceramic powder is not particularly limited, and for example, in the case of a conductive paste for an internal electrode of a multilayer ceramic capacitor, a known ceramic powder is appropriately selected depending on the type of multilayer ceramic capacitor to be applied. Examples of the ceramic powder include perovskite oxides containing Ba and Ti, and preferably barium titanate ( _BaTiO3 ).

The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent. The oxide may be an oxide of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, or one or more rare earth elements. The ceramic powder may be a perovskite-type oxide ferroelectric ceramic powder in which the Ba and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms, such as Sn, Pb, and Zr.

In the conductive paste for the internal electrodes, a powder having the same composition as the dielectric ceramic powder constituting the green sheet of the multilayer ceramic capacitor may be used as the ceramic powder. This suppresses the occurrence of cracks due to the mismatch of shrinkage at the interface between the dielectric layer and the internal electrode layer during the sintering process. In addition to the above, such ceramic powders include oxides such as ZnO, ferrite, PZT, BaO, Al ₂ O ₃ , Bi ₂ O ₃ , R (rare earth element) ₂ O ₃ , TiO ₂ , and Nd ₂ O _3. It is to be noted that one type of ceramic powder may be used, or two or more types may be used.

The number average particle diameter of the ceramic powder is, for example, 0.01 μm or more and 0.5 μm or less, and preferably 0.01 μm or more and 0.3 μm or less. When the ceramic powder has a number average particle diameter of 0.01 μm or more and 0.5 μm or less, it is possible to form a sufficiently fine, thin and uniform internal electrode when used as a conductive paste for internal electrodes. The number average particle diameter is a value determined by observation with a scanning electron microscope (SEM), and is the average value obtained by measuring the particle diameter of each of multiple particles from an image observed with an SEM at a magnification of 50,000 times.

The content of the ceramic powder is preferably 1 part by mass or more and 30 parts by mass or less, and more preferably 3 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the conductive powder. When the content of the conductive powder is 1 part by mass or more and 30 parts by mass or less, the conductivity and dispersibility are excellent.

The content of the ceramic powder is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, based on the total amount of the conductive paste. When the content of the conductive powder is 1% by mass or more and 20% by mass or less, the conductive paste has excellent conductivity and dispersibility.

<Vehicle>
The vehicle is specifically described in the section on [Vehicle], so a detailed description will be omitted here. The vehicle can be included in the conductive paste so that the content of the polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the conductive powder.

The binder resin content is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 6% by mass or less, based on the total amount of the conductive paste. When the binder resin content is 0.5% by mass or more and 10% by mass or less, the conductive paste has excellent conductivity and dispersibility. Therefore, the vehicle can be included in the conductive paste so that the binder resin content is 0.5% by mass or more and 10% by mass or less.

In the conductive paste of this embodiment, the ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound in the binder resin is 20 mass% or more, and preferably 30 mass% or more. If the ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound is less than 20 mass%, the suppression of phase separation will only occur in a part of the conductive paste, and the results may not be satisfactory. The ratio of the polymer compound to the total mass of the cellulose resin, polyvinyl acetal resin, and the polymer compound in the binder resin can be 99 mass% or less, or 95 mass%.

<Binder resin>
The conductive paste of this embodiment may further contain a binder resin in addition to the binder resin contained in the vehicle. Examples of the binder resin that can be contained include the same resin as the binder resin that can be contained in the vehicle, such as the polymer compound, cellulose resin, polyvinyl acetal resin, acrylic resin, maleic acid ester resin, etc. Details of these binder resins have already been described, so they will not be described here.

As already explained, the content of the polymer compound is preferably 1 part by mass to 10 parts by mass to 100 parts by mass of the conductive powder, more preferably 1 part by mass to 8 parts by mass, and the content of the binder resin is preferably 0.5% by mass to 10% by mass to 10% by mass, more preferably 1% by mass to 6% by mass, relative to the total amount of the conductive paste. Even when the conductive paste further contains a binder resin in addition to the vehicle, it is preferable that the total content of the binder resin in the conductive paste is within these ranges.

<Organic Solvent>
The conductive paste of this embodiment may further contain an organic solvent in addition to the organic solvent contained in the vehicle. Examples of organic solvents that can be contained include the same solvents as those that can be contained in the vehicle, and examples of solvents that can be used as a single solvent include isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate of the conductive paste, acetate-based solvents such as diethylene glycol monobutyl ether acetate, ether-based solvents such as ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and ethylene glycol dibutyl ether, terpene-based solvents such as dihydroterpinyl acetate and terpinyl acetate, hydrocarbon-based solvents such as tridecane, nonane, and cyclohexane, and petroleum-based hydrocarbon solvents such as mineral spirits. The organic solvent may be used alone or in a mixed solvent of two or more types.

The solvent contained in the conductive paste of this embodiment has an HSP δh of 6.5 MPa ^0.5 or less, preferably 6 MPa ^0.5 or less, and more preferably 5.5 MPa ^0.5 or less. In addition, in a mixed solvent composed of multiple solvents, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, diethylene glycol monobutyl ether acetate, terpineol, and dihydroterpineol may be added, provided that the HSP δh value is 6.5 MPa ^0.5 or less.

The content of the organic solvent is preferably 40 parts by mass or more and 100 parts by mass or less, and more preferably 65 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the conductive powder. When the content of the organic solvent is 40 parts by mass or more and 100 parts by mass or less, the conductivity and dispersibility are excellent. Note that this range of the content of the organic solvent is the same not only when only the organic solvent contained in the vehicle is used in the conductive paste, but also when an organic solvent is further contained in the conductive paste in addition to the organic solvent contained in the vehicle.

The organic solvent content is preferably 20% by mass or more and 60% by mass or less, and more preferably 35% by mass or more and 55% by mass or less, based on the total amount of the conductive paste. When the organic solvent content is 20% by mass or more and 60% by mass or less, the conductive paste has excellent conductivity and dispersibility. Note that this range of organic solvent content is the same not only when only the organic solvent contained in the vehicle is used in the conductive paste, but also when the conductive paste contains an organic solvent in addition to the organic solvent contained in the vehicle.

<Dispersant>
The conductive paste of the present embodiment may contain a dispersant. The role of the dispersant is to adsorb to the surface of the inorganic powder (conductive powder and ceramic powder) to suppress aggregation between the inorganic powders, or to improve the wettability of the organic vehicle to the inorganic powder to disperse the inorganic powder in the conductive paste. The dispersant (surfactant, etc.) may include an acid dispersant including a higher fatty acid, a polymer surfactant, etc., a cationic dispersant other than the acid dispersant, a nonionic dispersant, an amphoteric surfactant, and a polymer dispersant.

Furthermore, one or more types of dispersing agent may be selected, and the content of the conductive paste may be appropriately selected taking into consideration the viscosity, stickiness, and long-term storage stability of the conductive paste, and may be included within a range that does not impair the effects of the present invention.

The mass average molecular weight of the dispersant is preferably 200 to 100,000. More preferably, it is 300 to 30,000. If the mass average molecular weight is less than 200, the particles may not obtain sufficient electrostatic repulsion, and the dispersibility and storage stability of the particles may decrease. Normally, the dispersant is adsorbed to the particle surface to form an adsorption layer of the dispersant, and electrostatic repulsion and steric repulsion are imparted to the particles, thereby obtaining a paste with excellent dispersibility. However, it is thought that the repulsion of the adsorption layer is overcome by collisions between the particles over time, causing the particles to aggregate, so the mass average molecular weight is preferably 200 or more. If the mass average molecular weight is more than 100,000, the compatibility with the organic vehicle and organic solvent may decrease, particles may aggregate, and dispersibility and storage stability may decrease. In addition, the viscosity of the conductive paste may increase.

The amount of dispersant added is preferably 0.01 to 5.00 parts by mass, and more preferably 0.20 to 2.00 parts by mass, per 100 parts by mass of conductive metal powder. If the amount of dispersant is less than 0.01 parts by mass, it tends to be difficult to obtain sufficient dispersibility. On the other hand, if the amount exceeds 5.00 parts by mass, the drying properties become poor and problems such as a decrease in the dry film density occur.

The polymer dispersant is anionic and preferably has a carboxyl group or a carboxylic anhydride group. By using an anionic polymer dispersant, the dispersibility of inorganic powders such as conductive powders and ceramic powders in an organic vehicle can be further improved. Here, the carboxylic anhydride group refers to a state in which H ₂ O is dehydrated from two carboxyl groups to form an anhydride state. For example, acid anhydrides such as phthalic anhydride and maleic anhydride are included, and are molecular units formed from two carboxyl groups in a dehydrated state.

Anionic polymer dispersants are preferably provided with graft chains. Graft chains are also expected to improve solubility in various organic solvents.

The mass average molecular weight of the anionic polymer dispersant is preferably 1,000 to 100,000, more preferably 5,000 to 70,000, and even more preferably 10,000 to 60,000. By making the mass average molecular weight of the polymer dispersant 1,000 or more, the dispersibility of the inorganic powder in the organic vehicle can be improved. If the mass average molecular weight is greater than 100,000, the compatibility with the organic vehicle and organic solvent may decrease, particles such as conductive powder and ceramic powder may aggregate with each other, and the dispersibility and storage stability may decrease.

Such polymer dispersants have carboxy groups or carboxylic anhydride groups as functional groups on the main chain. For anionic polymer dispersants, it is desirable to further provide oxyethylene groups on the graft chains from the viewpoint of adsorption to inorganic powders.

The anionic polymer dispersant may contain one or more types. In other words, multiple types of polymer dispersants may be included depending on the length of the main chain, the length of the graft chain, the presence or absence of a graft chain, etc. The content of the anionic polymer dispersant in the conductive paste may be appropriately selected taking into consideration the viscosity, stickiness, long-term storage stability, etc. of the conductive paste, and may be included within a range that does not impair the effects of the present invention.

Furthermore, the conductive paste of this embodiment may contain a dispersant in addition to the anionic polymer dispersant. For example, the dispersant (surfactant, etc.) may include an acid dispersant including higher fatty acid, phosphoric acid, polymer surfactant, etc., a cationic dispersant other than the acid dispersant, a nonionic dispersant, an amphoteric surfactant, and a polymer dispersant.

The amount of dispersant contained in the conductive paste can be appropriately selected taking into consideration the viscosity, stickiness, and long-term storage stability of the conductive paste, and may be contained within a range that does not impair the effects of the present invention.

In addition, for both anionic polymer dispersants and other dispersants, the mass average molecular weight of the dispersant is preferably 200 to 100,000. More preferably, it is 300 to 30,000. If the mass average molecular weight is less than 200, the dispersibility and storage stability of the particles may decrease. Normally, the dispersant is adsorbed to the particle surface to form an adsorption layer of the dispersant, and electrostatic repulsion and steric repulsion are imparted to the particles, thereby obtaining a paste with excellent dispersibility. However, it is thought that over time, due to collisions between particles, the cohesive force of the particles exceeds the repulsive force of the adsorption layer, causing the particles to aggregate, so the mass average molecular weight is preferably 200 or more. In addition, if the mass average molecular weight is more than 100,000, the compatibility with the organic vehicle and organic solvent may decrease, particles may aggregate, and dispersibility and storage stability may decrease. In addition, the problem of high paste viscosity may occur.

The total amount of anionic polymer dispersant and other dispersant added is preferably 0.01 to 5.00 parts by mass, and more preferably 0.20 to 2.00 parts by mass, per 100 parts by mass of conductive metal powder. If the amount of dispersant is less than 0.01 parts by mass, it tends to be difficult to obtain sufficient dispersibility. On the other hand, if it exceeds 5.00 parts by mass, the drying property becomes poor and problems such as a decrease in the dry film density occur.

(Other additives)
Furthermore, in order to impart flexibility to a dried film obtained from the conductive paste, a known additive such as a plasticizer can be added to the conductive paste.

(Method of manufacturing conductive paste)
The method for producing the conductive paste of this embodiment is not particularly limited, and a conventionally known method can be used. The conductive paste can be produced, for example, by preparing the above-mentioned components and stirring and kneading them with a three-roll mill, a ball mill, a mixer, or the like. In this case, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder is sufficiently loosened without agglomeration, and the dispersant is distributed over the surface, making it easy to obtain a uniform conductive paste. Alternatively, the binder resin may be dissolved in an organic solvent for a vehicle to produce an organic vehicle, and the conductive powder, ceramic powder, organic vehicle, and dispersant may be added to the organic solvent for the paste, and the mixture may be stirred and kneaded with a mixer to produce the conductive paste.

In order to improve the compatibility of the organic vehicle, it is preferable to use the same organic solvent for the paste that adjusts the viscosity of the conductive paste. The content of the organic solvent for the vehicle is, for example, 5 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the conductive powder. In addition, the content of the organic solvent for the vehicle is preferably 10% by mass or more and 40% by mass or less with respect to the total amount of the conductive paste.

The surface smoothness of the dried film formed by printing the conductive paste can be evaluated by the surface roughness. The surface roughness of the conductive paste can be measured, for example, by the method described in the examples (method of measuring the arithmetic mean height Sa based on the ISO 25178 standard using a Keyence VK-X120). When the surface smoothness of the dried film is evaluated by the arithmetic mean height Sa, the value is preferably 0.10 μm or less. If the surface roughness is 0.10 μm or less by the method described in the examples, a low surface roughness can be achieved even after printing and drying on a green sheet. Considering the manufacturing process of a multilayer ceramic capacitor, if the surface roughness of the dried film of the conductive paste is low, the dried film of the conductive paste will adhere to the green sheet as a surface, and the adhesion between the dried film of the conductive paste and the green sheet will be excellent. Therefore, it is desirable for the surface roughness of the dried film of the conductive paste to be lower.

[Electronic components, multilayer ceramic capacitors]
The conductive paste of the present invention can be suitably used in electronic components such as multilayer ceramic capacitors. The multilayer ceramic capacitor has dielectric layers formed using green sheets and internal electrode layers formed using the conductive paste.

In a multilayer ceramic capacitor, it is preferable that the dielectric ceramic powder contained in the green sheet and the ceramic powder contained in the conductive paste are powders of the same composition, for example, barium titanate can be used. In a multilayer ceramic capacitor manufactured using the conductive paste of this embodiment, sheet attack and peeling failure of the green sheet are suppressed even when the thickness of the green sheet is, for example, 3 μm or less.

Below, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, the components may be shown diagrammatically or at a different scale as appropriate. The positions and directions of components will be described with reference to the XYZ Cartesian coordinate system shown in Figures 1A and 1B as appropriate. In this XYZ Cartesian coordinate system, the X and Y directions are horizontal directions, and the Z direction is vertical (up and down) directions.

1A and 1B are a perspective view and a side cross-sectional view of a multilayer ceramic capacitor 1, which is an example of an electronic component according to an embodiment. The multilayer ceramic capacitor 1 includes a ceramic laminate 10 in which dielectric layers 12 and internal electrode layers 11 are alternately stacked, and an external electrode 20.

Below, a method for manufacturing the multilayer ceramic capacitor 1 using the above-mentioned conductive paste is described. First, the conductive paste is printed on a dielectric layer made of a green sheet and dried to form a dry film. A plurality of dielectric layers having this dry film on their upper surfaces are stacked and pressed together to obtain a laminate, which is then fired and integrated to produce a ceramic laminate 10 in which internal electrode layers 11 and dielectric layers 12 are alternately stacked. A pair of external electrodes 20 are then formed on both ends of the ceramic laminate 10 to manufacture the multilayer ceramic capacitor 1. A more detailed description is given below.

First, a green sheet is prepared, which is an unfired ceramic sheet made of a dielectric material. For example, this green sheet can be prepared by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a powder of a specific ceramic raw material such as barium titanate to obtain a dielectric layer paste, which is then applied in sheet form onto a support film such as a PET film, and dried to remove the solvent. The thickness of the dielectric layer made of the green sheet is not particularly limited, but is preferably 0.05 μm or more and 3 μm or less in view of the demand for miniaturization of multilayer ceramic capacitors.

Next, the above-mentioned conductive paste is printed (applied) on one side of this green sheet by a known method such as screen printing, and then dried to form a dry film, to prepare multiple sheets. Note that, from the viewpoint of the requirement to make the internal electrode layer 11 thinner, it is preferable that the thickness of the printed conductive paste (dry film) is set to a thickness such that the thickness of the dry film after drying is 1 μm or less.

Then, the green sheet is peeled off from the support film, and the dielectric layers made of the green sheet and the dry film formed on one side of the green sheet are alternately stacked, and then a laminate is obtained by heating and pressurizing. Note that a configuration in which protective green sheets not coated with conductive paste are further placed on both sides of the laminate may also be used.

Next, the laminate is cut to a predetermined size to form a green chip, and then the green chip is subjected to a binder removal treatment and fired under a reducing atmosphere to manufacture the ceramic laminate 10. The binder removal treatment is preferably performed in air or _N2 gas atmosphere. The temperature during the binder removal treatment is, for example, 200°C or higher and 400°C or lower. The temperature is preferably held for 0.5 hours or longer and 24 hours or shorter during the binder removal treatment. The firing is performed in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layer, and the temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature is preferably held for 0.5 hours or longer and 8 hours or shorter.

By firing the green chip, the organic binder in the green sheet is completely removed and the ceramic raw powder is fired to form the ceramic dielectric layer 12. The organic vehicle in the dry film is also removed, and the nickel powder or nickel-based alloy powder is sintered or melted and integrated to form the internal electrode layer 11, forming a multilayer ceramic sintered body in which multiple dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that the sintered multilayer ceramic sintered body may be annealed to incorporate oxygen into the dielectric layer to increase reliability and suppress reoxidation of the internal electrodes.

Then, a pair of external electrodes 20 are provided on the produced multilayer ceramic sintered body to manufacture the multilayer ceramic capacitor 1. For example, the external electrode 20 includes an external electrode layer 21 and a plating layer 22. The external electrode layer 21 is electrically connected to the internal electrode layer 11. Note that, for example, copper, nickel, or an alloy thereof can be suitably used as the material for the external electrode 20. Note that the electronic component is not limited to a multilayer ceramic capacitor, and may be an electronic component other than a multilayer ceramic capacitor, such as a varistor.

The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited in any way by these examples.

[Preparation of vehicle]
As described below, a cellulose-based compound and a polyvinyl acetal-based compound were synthesized, and then these were bonded to synthesize a polymer compound, thereby preparing a vehicle.

(Synthesis of Cellulosic Compound (1a) Having a Vinyl Group)
Ethyl cellulose (Dow Chemical's "Ethocel STD-100", number average molecular weight Mn (standard polystyrene equivalent value by GPC): 63,420, average number of unetherified hydroxyl groups among hydroxyl groups in one cyclic structure of glucose ring: 0.48) was prepared and dried. The ethyl cellulose was dried in order to remove moisture adsorbed by the ethyl cellulose. Drying was performed under reduced pressure at room temperature.

100 parts by mass of the dried ethyl cellulose was dissolved in 900 parts by mass of ethyl acetate to obtain a solution. 0.17 parts by mass of 3-allyloxypropionic acid, which corresponds to an average of one vinyl group introduced per molecule of ethyl cellulose, 0.20 parts by mass of diisopropylcarbodiimide as a condensing agent, and 0.004 parts by mass of dimethylaminopyridine as a reaction accelerator were added to the obtained solution, and the reaction was carried out by stirring at a temperature of 40°C for 5 hours. The ethyl acetate was then removed to obtain a cellulose-based compound (1a) in which a vinyl group was introduced into ethyl cellulose as a solid.

A portion of the resulting solid was analyzed by FT-IR and 1H-NMR, confirming the formation of ester bonds and that the same molar amount of vinyl groups as the charged 3-allyloxypropionic acid had been introduced into the ethyl cellulose.

In addition to the compound in which a vinyl group has been introduced into ethyl cellulose, the cellulose-based compound (1a) also contains unreacted ethyl cellulose, and in the examples, this mixture is referred to as the cellulose-based compound (1a). The same applies to the cellulose-based compound (2a) described below.

(Synthesis of polyvinyl butyral compound (1b) having thiol group)
Polyvinyl butyral ("BM-SZ" manufactured by Sekisui Chemical Co., Ltd., number average molecular weight Mn (standard polystyrene equivalent value by GPC): 55,000, hydroxyl group amount: about 22 mol%) was prepared and dried. The polyvinyl butyral was dried in order to remove moisture adsorbed by the polyvinyl butyral. Drying was performed under reduced pressure at room temperature. 100 parts by mass of the dried polyvinyl butyral was dissolved in 900 parts by mass of ethyl acetate. 0.20 parts by mass of 3-mercaptopropionic acid, which corresponds to an average of one thiol group introduced per molecule of polyvinyl butyral, 0.24 parts by mass of diisopropylcarbodiimide as a condensing agent, and 0.005 parts by mass of dimethylaminopyridine as a reaction accelerator were added to the obtained solution, and the mixture was stirred at a temperature of 40° C. for 5 hours to carry out a reaction. Thereafter, the ethyl acetate was removed to obtain a polyvinyl butyral-based compound (1b) in which a thiol group was introduced into polyvinyl butyral as a solid.

A portion of the resulting solid was analyzed by FT-IR and 1H-NMR, confirming the formation of ester bonds and that the same molar amount of thiol groups as the charged 3-mercaptopropionic acid had been introduced into the polyvinyl butyral.

In addition, the polyvinyl butyral-based compound (1b) contains unreacted polyvinyl butyral in addition to the compound in which a thiol group has been introduced into polyvinyl butyral, and in the examples, this mixture is referred to as polyvinyl butyral-based compound (1b). The same applies to the polyvinyl butyral-based compound (2b) described below.

(Synthesis of Cellulosic Compound (2a) Having Vinyl Group)
A cellulose compound (2a) was synthesized in the same manner as for the cellulose compound (1a), except that an average of two 3-allyloxypropionic acid units were added per molecule of ethyl cellulose.

(Synthesis of polyvinyl butyral compound (2b) having thiol group)
Polyvinyl butyral compound (2b) was synthesized in the same manner as polyvinyl butyral compound (1b), except that 3-mercaptopropionic acid was added in an amount equivalent to an average of two molecules per molecule of polyvinyl butyral.

(Preparation of Vehicle 1)
5 parts by mass of cellulose compound (1a) and 4.35 parts by mass of polyvinyl butyral compound (1b) were dissolved in 60 parts by mass of isobornyl acetate as a solvent, and the solution was transferred to a glass flask reaction vessel, and after nitrogen substitution, 0.1 parts by mass of azobisisobutyronitrile was added as a radical generator to the solution, and the reaction was carried out at 80°C for 3 hours while stirring to obtain a vehicle 1 containing polymer compound 1. Here, the cellulose compound (1a) and the polyvinyl butyral compound (1b) have the same molar number. The vehicle 1 contains 13.5% by mass of polymer compound 1. Here, polymer compound 1 is a mixture of a polymer compound in which cellulose compound (1a) and polyvinyl butyral compound (1b) are bonded, unreacted ethyl cellulose, and unreacted polyvinyl butyral, and in the examples, these mixtures are referred to as polymer compound 1. The δh of the HSP of isobornyl acetate is 3.0 MPa ^0.5 .

When the synthesized polymer compound 1 was analyzed by FT-IR and 1H-NMR, -S- bonds were confirmed, and the target structure was obtained. In addition, the mass average molecular weight (Mw: standard polystyrene equivalent value by GPC) of polymer compound 1 was measured. The δh of the HSP of polymer compound 1 was calculated to be 7.61 MPa ^0.5 by HSPiP version 5 from the HSP values of the soluble solvents after conducting a test to dissolve the resin in 20 types of solvents with known HSP values.

(Preparation of Vehicle 2)
Polymer compound 2 synthesized from a cellulose compound (2a) and a polyvinyl butyral compound (2b) was also synthesized in the same manner as polymer compound 1 to obtain a vehicle 2. The content of polymer compound 2 in vehicle 2 was 13.5% by mass. Polymer compound 2 is a mixture of a polymer compound in which a cellulose compound (2a) and a polyvinyl butyral compound (2b) are bonded together, as in polymer compound 1, and unreacted ethyl cellulose and unreacted polyvinyl butyral, and in the examples, a mixture of these is referred to as polymer compound 2.

Similarly to polymer compound 1, the synthesized polymer compound 2 was analyzed by FT-IR and 1H-NMR, and -S- bonds were confirmed, and the target structure was obtained. The mass average molecular weight (Mw: standard polystyrene equivalent value by GPC) of polymer compound 2 was measured. The δh of HSP of polymer compound 2 was calculated by the same method as polymer compound 1, and was 7.63 MPa ^0.5 .

(Preparation of Vehicle 3)
5 parts by mass of the cellulose compound (1a) and 4.35 parts by mass of the polyvinyl butyral compound (1b) were dissolved in 60 parts by mass of the solvent dihydroterpineol, and the solution was transferred to a glass flask reaction vessel. After nitrogen substitution, 0.1 parts by mass of azobisisobutyronitrile was added to the solution as a radical generator, and the solution was reacted at 80° C. for 3 hours while stirring to obtain a vehicle 3 containing a polymer compound 3. Here, the cellulose compound (1a) and the polyvinyl butyral compound (1b) have the same molar number. The vehicle 3 contains 13.5% by mass of the polymer compound 3. Here, the polymer compound 3 is a mixture of a polymer compound in which the cellulose compound (1a) and the polyvinyl butyral compound (1b) are bonded, unreacted ethyl cellulose, and unreacted polyvinyl butyral, and in the examples, these mixtures are referred to as the polymer compound 3. The δh of the HSP of dihydroterpineol is 6.7 MPa ^0.5 .

Similarly to polymer compound 1, the synthesized polymer compound 3 was analyzed by FT-IR and 1H-NMR, and -S- bonds were confirmed, and the target structure was obtained. The mass average molecular weight (Mw: standard polystyrene equivalent value by GPC) of polymer compound 3 was measured. The δh of HSP of polymer compound 3 was calculated by the same method as polymer compound 1, and was 7.62 MPa ^0.5 .

Table 1 shows the characteristics of the cellulose compounds (1a) and (2a) and the polyvinyl acetal compounds (1b) and (2b) used in the polymer compounds 1 to 3 contained in the vehicles 1 to 3, and Table 2 shows the mass average molecular weights of the polymer compounds 1 to 3, as well as the names and δh values of the organic solvents contained in the vehicles 1 to 3.

[Example 1]
Example 1 is an example in which a conductive paste was prepared using vehicle 1 as follows, and the obtained conductive paste was used to evaluate physical properties such as sheet attack, surface roughness, and dry film density. Here, vehicle 1 contains polymer compound 1, in which a cellulose compound and a polyvinyl acetal compound are bonded by sulfur atoms, as a binder resin, and also contains isobornyl acetate, whose Hansen solubility parameter hydrogen bond term δh is 3.0 MPa ^0.5 (6.5 MPa ^0.5 or less), as an organic solvent. In polymer compound 1, the molar ratio of sulfur atoms to the cellulose compound is 1.

Preparation of Conductive Paste
The conductive paste of Example 1 was prepared by mixing 47% by mass of Ni powder, 4.7% by mass of ceramic powder, 26.67% by mass of vehicle 1, 0.4% by mass of an anionic dispersant of an amide compound of amino acid and fatty acid (hereinafter, may be referred to as "dispersant A"), and 21.23% by mass of the remaining organic solvent (isobornyl acetate) to make a total of 100% by mass.

(conductive powder)
The conductive powder used in preparing the conductive paste was Ni powder (number average particle size of 0.2 μm as measured by SEM).

(ceramic powder)
The ceramic powder used in preparing the conductive paste was barium titanate (BaTiO ₃ , number average particle size measured by SEM: 0.05 μm).

[Evaluation method]
(Sheet attack, surface roughness of dried film, dry film density)
The sheet attack of the prepared conductive paste, the surface roughness of the dried film obtained by drying the conductive paste, and the dry film density were evaluated as follows.

<Seat Attack>
The conductive paste was printed on a 2 μm thick green sheet (containing barium titanate (BT, BaTiO ₃ ) and polyvinyl butyral resin) and dried at 80° C. for 3 minutes. Immediately after drying, the surface of the green sheet on the reverse side of the printed surface was observed under a microscope to check for the presence or absence of the swelling phenomenon specific to sheet attack. If no swelling phenomenon was observed, it was rated as ○ (good), and if it was observed, it was rated as × (bad).

<Surface roughness>
The conductive paste thus prepared was screen-printed on a 2.54 cm (1 inch) square heat-resistant tempered glass and dried at 120°C in air for 1 hour to prepare a 20 mm square dry film with a thickness of 1 to 3 μm. When the conductive paste has good dispersibility, the surface of the dry film is smooth. When the dispersibility is poor, aggregation occurs in the conductive paste, the surface of the dry film becomes rough, and the surface smoothness decreases. Therefore, the surface roughness Sa (arithmetic mean height) of the prepared dry film was measured based on the ISO 25178 standard using a laser microscope (Keyence VK-X120). The smaller the value of the surface roughness Sa (arithmetic mean height), the smoother the surface of the dry film.

<Dry film density>
The conductive paste thus prepared was placed on a PET film and spread to a length of about 100 mm using an applicator with a width of 50 mm and a gap of 125 μm. The obtained PET film was dried at 120° C. for 40 minutes to form a dried body, which was then cut into four pieces of 2.54 cm (1 inch) square. After removing the PET film, the thickness and weight of each of the four dried films were measured to calculate the dry film density (average value).

[Comparative Example 1]
Comparative Example 1 is an example in which a conductive paste was prepared in the same manner as in Example 1 using Vehicle 2, and the obtained conductive paste was used to evaluate physical properties such as sheet attack, surface roughness, and dry film density. Here, Vehicle 2 contains Polymer Compound 2, in which a cellulose compound and a polyvinyl acetal compound are bonded by sulfur atoms, as a binder resin, and also contains isobornyl acetate, whose Hansen solubility parameter hydrogen bond term δh is 3.0 MPa ^0.5 (6.5 MPa ^0.5 or less), as an organic solvent. In Polymer Compound 2, the molar ratio of sulfur atoms to the cellulose compound is 2.

<Preparation of conductive paste and evaluation of physical properties>
A conductive paste according to Comparative Example 1 was prepared in the same manner as in Example 1, except that Vehicle 2 was used, and the sheet attack, surface roughness of the dried film, and density of the dried film were evaluated in the same manner as in Example 1.

[Comparative Example 2]
Comparative Example 2 is an example in which a conductive paste was prepared in the same manner as in Example 1 using vehicle 3, and the obtained conductive paste was used to evaluate physical properties such as sheet attack, surface roughness, and dry film density. Here, vehicle 3 contains polymer compound 3, in which a cellulose compound and a polyvinyl acetal compound are bonded by sulfur atoms, as a binder resin, and also contains dihydroterpineol, whose Hansen solubility parameter hydrogen bond term δh is 6.7 MPa ^0.5 , as an organic solvent. In polymer compound 3, the molar ratio of sulfur atoms to the cellulose compound is 3.

A conductive paste for Comparative Example 2 was prepared in the same manner as in Example 1, except that dihydroterpineol was used as the vehicle 3 and the remaining organic solvent, and the sheet attack, surface roughness of the dried film, and density of the dried film were evaluated in the same manner as in Example 1.

[Comparative Example 3]
Comparative Example 3 is an example in which a conductive paste was prepared using ethyl cellulose and polyvinyl butyral resin without using any of the vehicles 1 to 3 and without including any polymer compound, and the obtained conductive paste was used to evaluate physical properties such as sheet attack, surface roughness, dry film density, etc. In addition, isobornyl acetate, which has a hydrogen bond term δh of the Hansen solubility parameter of 3.0 MPa ^0.5 (6.5 MPa ^0.5 or less), was used as the organic solvent to prepare the conductive paste.

(Preparation of Vehicle 4a)
Five parts by mass of ethyl cellulose (Ethocel STD-100 manufactured by Dow Chemical) was dissolved in 30 parts by mass of isobornyl acetate to prepare an organic vehicle 4a.

(Preparation of Vehicle 4b)
A vehicle 4b was prepared by dissolving 4.35 parts by mass of polyvinyl butyral resin ("BM-SZ" manufactured by Sekisui Chemical Co., Ltd.) in 30 parts by mass of isobornyl acetate.

(Preparation of Vehicle 4)
Organic vehicle 4 was prepared by mixing organic vehicle 4a and organic vehicle 4b in equal amounts.

Preparation of Conductive Paste
The conductive paste of Comparative Example 3 was prepared by mixing 47% by mass of Ni powder, 4.7% by mass of ceramic powder, 26.67% by mass of vehicle 4, 0.4% by mass of dispersant A, and 21.23% by mass of the remaining organic solvent (isobornyl acetate) to a total of 100% by mass.

The conductive paste thus prepared was used to evaluate the sheet attack, surface roughness of the dried film, and density of the dried film in the same manner as in Example 1.

[Comparative Example 4]
Comparative Example 4 is an example in which a conductive paste was prepared using ethyl cellulose and polyvinyl butyral resin without using any of the vehicles 1 to 3 and without including any polymer compound, and the obtained conductive paste was used to evaluate physical properties such as sheet attack, surface roughness, dry film density, etc. In addition, dihydroterpineol with a hydrogen bond term δh of the Hansen solubility parameter of 6.7 MPa ^0.5 was used as the organic solvent to prepare the conductive paste.

(Preparation of Vehicle 5a)
Five parts by mass of ethyl cellulose (Ethocel STD-100 manufactured by Dow Chemical) was dissolved in 30 parts by mass of dihydroterpineol to prepare an organic vehicle 5a.

(Preparation of Vehicle 5b)
Vehicle 5b was prepared by dissolving 4.35 parts by mass of polyvinyl butyral resin ("BM-SZ" manufactured by Sekisui Chemical Co., Ltd.) in 30 parts by mass of dihydroterpineol.

(Preparation of Vehicle 5)
Organic vehicle 5 was prepared by mixing equal amounts of vehicle 5a and organic vehicle 5b.

Preparation of Conductive Paste
The conductive paste of Comparative Example 4 was prepared by mixing 47% by mass of Ni powder, 4.7% by mass of ceramic powder, 26.67% by mass of vehicle 5, 0.4% by mass of dispersant A, and 21.23% by mass of the remaining organic solvent (dihydroterpineol) to make a total of 100% by mass.

The conductive paste thus prepared was used to evaluate the sheet attack, surface roughness of the dried film, and density of the dried film in the same manner as in Example 1.

Table 3 shows the names of the organic solvents contained in the conductive pastes in Example 1 and Comparative Examples 1 to 4, the δh values, the types of binder resins, and the evaluation results for sheet attack, surface roughness, and dry film density.

[Evaluation Results]
As shown in Table 3, the dry film formed with the conductive paste of Example 1 had a surface roughness Sa (arithmetic mean height) of 90 nm, which was the lowest compared to the comparative examples. The conductive paste of Example 1 also had a high dry film density of 5.51 g/ ^cm3 . Furthermore, the conductive paste of Example 1 did not cause sheet attack. In other words, the conductive paste of Example 1 did not cause sheet attack on the green sheet, and was able to form a dry film with good smoothness and dry film density.

On the other hand, in the case of the conductive paste of Comparative Example 1, in which the number of functional groups of the polymer compound 2 was 2, the surface roughness and dry film density of the obtained dried film were both inferior to those of Example 1. And in the case of the conductive paste of Comparative Example 3, which used common ethyl cellulose and polyvinyl butyral resin as the binder resin and used isobornyl acetate, a solvent that does not cause sheet attack, no sheet attack occurred, but the surface roughness was the worst among Example 1 and Comparative Examples 1 to 4. Also, in the case of the conductive paste of Comparative Example 4, which used common ethyl cellulose and polyvinyl butyral resin as the binder resin and used dihydroterpineol, sheet attack occurred, and the surface roughness and dry film density were inferior to those of Example 1.

The conductive paste according to this embodiment uses fine conductive powder or ceramic powder, and is free of sheet attack on the green sheet, has a smooth dry film, and is excellent in adhesion. Therefore, it can be suitably used as a raw material for the internal electrodes of multilayer ceramic capacitors, which are chip parts (electronic parts) in electronic devices such as mobile phones and digital devices, and is industrially useful.

REFERENCE SIGNS LIST 1 Multilayer ceramic capacitor 10 Ceramic laminate 11 Internal electrode layer 12 Dielectric layer 20 External electrode 21 External electrode layer 22 Plating layer

Claims (14)

A binder resin;
and an organic solvent,
the binder resin contains a polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded together through a sulfur atom,
the molar ratio of sulfur atoms contained in the polymer compound to the cellulose-based compound is 0.3 to 1.7;
The vehicle has a hydrogen bond term δh of the Hansen solubility parameter of the organic solvent of 6.5 MPa ^or less. The vehicle according to claim 1, wherein the polymer compound has a hydrogen bond term δh of Hansen solubility parameters of 6.5 to 8.5 MPa ^0.5. the cellulose-based compound is a cellulose derivative having a thiol group or a vinyl group,
the polyvinyl acetal compound is a polyvinyl acetal resin having a thiol group or a vinyl group,
When the cellulose derivative has a thiol group, the polyvinyl acetal resin has a vinyl group that reacts with the thiol group,
3. The vehicle according to claim 1, wherein when the cellulose derivative has a vinyl group, the polyvinyl acetal resin has a thiol group that reacts with the vinyl group. The cellulose derivative is ethyl cellulose having a thiol group or a vinyl group,
4. The vehicle of claim 3, wherein the polyvinyl acetal resin is a polyvinyl butyral having a thiol group or a vinyl group. the cellulose-based compound is a first esterification reaction product obtained by dehydration condensation of a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of cellulose,
The polyvinyl acetal compound is a second esterification product obtained by dehydration condensation of a carboxy group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of a polyvinyl acetal,
when the first esterification reactant comprises a thiol group, the second esterification reactant comprises a vinyl group;
when the first esterification reactant comprises a vinyl group, the second esterification reactant comprises a thiol group;
The vehicle according to claim 1 or 2, wherein the polymer compound is a thiol-ene reaction product of the first esterification reactant and the second esterification reactant. the first esterification reaction product is an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-allyloxypropionic acid and a hydroxyl group of ethyl cellulose,
6. The vehicle according to claim 5, wherein the second esterification reaction product is an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-mercaptopropionic acid and a hydroxyl group of polyvinyl butyral. A conductive paste comprising the vehicle according to claim 1 or 2, a conductive powder, and a ceramic powder,
The conductive paste, wherein the hydrogen bond term δh of the Hansen solubility parameter of the organic solvent in the conductive paste is 6.5 MPa ^0.5 or less. The conductive paste according to claim 7, wherein the number average particle size of the conductive powder is 0.05 μm or more and 1.0 μm or less. The conductive paste of claim 7, wherein the ceramic powder includes barium titanate. The conductive paste according to claim 7, wherein the number average particle size of the ceramic powder is 0.01 μm or more and 0.5 μm or less. The conductive paste according to claim 7, wherein the ceramic powder content is 1% by mass or more and 20% by mass or less. The conductive paste according to claim 7, which is for use in internal electrodes of multilayer ceramic components. An electronic component formed using the conductive paste described in claim 7. The laminate has at least a dielectric layer and an internal electrode layer stacked thereon,
8. A multilayer ceramic capacitor, wherein the internal electrode layers are formed using the conductive paste according to claim 7.