WO2024062857A1 - Electrically conductive paste, electronic component, and multilayer ceramic capacitor - Google Patents

Abstract

The present invention provides: an electrically conductive paste which uses an electrically conductive powder and a ceramic powder that are refined for the size reduction and thickness reduction of a multilayer ceramic electronic component, and which is capable of forming an internal electrode layer that exhibits excellent adhesive properties, while having a smooth dry film; an electronic component; and a multilayer ceramic capacitor.　The electrically conductive paste contains an electrically conductive powder, a ceramic powder, a dispersant, a binder resin and an organic solvent. The binder resin contains cellulose, a polyvinyl acetal, and a polymer compound which is obtained by bonding a cellulose compound and a polyvinyl acetal compound by means of sulfur atoms. The molar ratio of sulfur atoms contained in the polymer compound relative to the sum total of the cellulose and the cellulose compound is 0.3-1.7. The dispersant is an anionic polymer compound.

Description

Conductive paste, electronic components and multilayer ceramic capacitors

The present invention relates to 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.

A multilayer ceramic capacitor is manufactured, for example, as follows. First, conductive paste for internal electrodes is printed (applied) in a predetermined electrode pattern on the surface of a green sheet containing dielectric powder such as barium titanate (BaTiO ₃ ) and binder resin such as polybutyral resin. , and dry to form a dry film. Next, a laminate is formed in which the dry films and green sheets are alternately stacked and heat-pressed to form an integrated state. This laminate is cut, subjected to an organic binder removal treatment in an oxidizing atmosphere or an inert atmosphere, and then fired to obtain fired chips. Next, an external electrode paste is applied to both ends of the fired chip, and after firing, nickel plating or the like is applied to the external electrode surface to obtain a multilayer ceramic capacitor (MLCC).

In recent years, MLCCs have been required to be even smaller and have a larger capacity. For example, for internal electrodes using nickel, thinner electrode films with excellent density and continuity, and ceramic dielectric materials and their use are required. Regarding the dielectric layer used in the prior art, attempts are being made to increase the dielectric constant and make the layer thinner, and dielectric layers with a thickness of 1.0 μm or less have already been put into practical use. It is also desired that the electrode film has a thickness of 1.0 μm or less.

The required characteristics for increasing the size and capacity of MLCCs include suppressing the decrease in insulation resistance under high temperature and high voltage, that is, high reliability. The decrease in insulation resistance is said to be caused by the fact that the surface of the Ni electrode layer sandwiching the dielectric layer becomes uneven during the firing process, and the electric field concentrates on the protrusions. In the firing process, the Ni electrode layer is formed through a process in which the Ni powder is sintered and becomes densified. However, since fine Ni powder sinters quickly, the electrode is likely to break off and become spheroidized. As a result, the effective electrode area of the Ni electrode layer decreases, leading to a decrease in capacity, and the unevenness on the surface of the Ni electrode layer leads to a decrease in insulation resistance.

When MLCC becomes thinner, the adhesion between the green sheet and the internal electrode layer decreases, causing problems such as frequent peeling and lamination misalignment due to insufficient adhesion during lamination. paste is used. However, plasticizers cause a noticeable decrease in the elastic modulus of the printed film, causing it to soften and become easily deformed, so even if the adhesion to the green sheet is improved, problems such as poor cutting of the internal electrode layer become serious. Furthermore, the plasticizer increases the amount of gas generated in the organic binder removal process, which causes cracks.

When stacking ceramic green sheets and pressing them in the thickness direction, if the adhesion between the green sheets is weak, the adhesion between the green sheets will be poor. This poor adhesion can lead to short-circuit defects, for example, in multilayer ceramic capacitors. In particular, due to the demand for multi-layered MLCCs, it is necessary to reduce the thickness of each dielectric layer by using fine particles of dielectric powder and increase the number of laminated layers, so it is necessary to improve adhesion defects. is desired. If the adhesion between the green sheets is weak, structural defects such as delamination, voids, and cracks occur during firing, reducing the yield of MLCC.

In order to improve such adhesion defects, the following measures 1) and 2) can be considered.
1) It is possible to increase the amount of binder or tackifier in the conductive paste, but simply increasing the amount of these does not significantly improve adhesion. Conversely, if the amount of these is increased, the amount of organic substances such as organic binders and tackifiers added to the conductive paste will increase, and these organic substances will make it difficult to remove the organic binder. Even after the treatment, the organic matter (residual carbon) that remains may cause structural defects in the subsequent firing treatment.
2) When laminating multiple ceramic green sheets on which conductive paste films are formed, the surface of the coating film made of conductive paste is smoothed to increase the contact area between the conductive paste film and the ceramic green sheets. As a result, adhesion can be improved.

Although the purpose of improving the adhesion between the internal electrode and the green sheet is to prevent cracking, using butyral resin as the resin can prevent the electrode from peeling off during cutting. Until now, cellulose resins such as ethyl cellulose have been mainly used as organic binders, but cellulose resins have high compatibility with various solvents and are effective in imparting the desired rheological properties to conductive pastes. On the other hand, since the conductive paste itself does not have much thermoplasticity, it has the disadvantage that the dried part of the conductive paste hardly maintains adhesion to the upper green sheet during thermocompression bonding. As a result, it is possible to further improve the thermocompression adhesion between the internal electrodes of the green sheet, which is conventionally screen-printed with conductive paste, and the green sheet on top of the green sheet, to prevent misalignment of the electrodes inside the chip, and to improve electrode alignment. At the same time, it has not yet been possible to obtain a conductive paste for internal electrodes of multilayer ceramic capacitors that can prevent chips from cracking or peeling and that can accommodate high lamination.

Therefore, the internal electrode paste may contain an organic resin, and the organic binder resin is preferably a mixture of ethyl cellulose (EC) and polyvinyl butyral (PVB).

Ethylcellulose (EC) has good solubility in solvents, printability, combustion decomposability, etc., and therefore can be suitably used as a binder for paste for internal electrodes. Further, by using polyvinyl butyral (PVB), which is used for green sheets, as an organic binder resin, it is possible to increase the adhesion strength between the green sheets and the dry film of the paste for internal electrodes.

Patent Documents 1 and 2 disclose a conductive paste containing a cellulose resin and a polyvinyl butyral resin as a binder resin, and disclose that the adhesiveness with ceramic green sheets is improved.

Patent No. 5299904 Patent No. 5224722

However, when two different organic binder resins are generally mixed, most of the combinations are incompatible (incompatible). In the case of a combination of two organic binder resins that are incompatible, the two organic binder resins basically do not dissolve and exist independently, so not only will the expected performance not be achieved, but the functionality will often deteriorate significantly. .

Furthermore, if the resin becomes difficult to dissolve in the solvent, the smoothness of the dried paste film will deteriorate. For example, when EC and PVB are mixed, a typical "sea-island structure" is observed, confirming phase separation. As a result, the distribution of inorganic particles (conductive particles, ceramic powder) in the dry film becomes uneven. In this way, the combination of organic materials in the paste composition affects the dispersibility of inorganic particles (conductive particles, ceramic powder) in the dry film.

By making polymers that do not normally mix together compatible with each other, it is possible to combine the characteristics of both polymers, stabilize the interface between the different polymers, and achieve a uniform and stable dispersion state.

Furthermore, since the conductive pastes disclosed in Patent Documents 1 and 2 contain polyvinyl butyral resin, it is possible to improve the adhesion between the dry film and the green sheet. However, since these technologies use cellulose resin and polyvinyl butyral resin together, the dispersion of the conductive powder and ceramic powder in the conductive paste is insufficient due to poor compatibility between the two resins. In some cases, the density and smoothness of the dried film of the conductive paste were insufficient. The characteristics of such a dry film cannot be said to be sufficient to cope with the increase in capacitance of multilayer ceramic capacitors in recent years.

In light of these circumstances, the present invention aims to provide a conductive paste using fine conductive powder or ceramic powder for making multilayer ceramic electronic components smaller and thinner, which has a smooth dry film and can form an internal electrode layer with excellent adhesion, as well as an electronic component and a multilayer ceramic capacitor.

In order to solve the above problems, the conductive paste of the present invention includes a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, and the binder resin contains cellulose, polyvinyl acetal, A polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded by a sulfur atom is included, and the molar ratio of the sulfur atom contained in the polymer compound to the total of the cellulose and the cellulose compound is 0.3 to 1.7, and the dispersant is an anionic polymer compound.

The dispersant may include a carboxy group or a carboxylic acid anhydride group.

When the cellulose compound is a cellulose derivative having a thiol group or a vinyl group, and the polyvinyl acetal compound is a polyvinyl acetal resin having a thiol group or a vinyl group, and the cellulose derivative has a thiol group, The polyvinyl acetal resin may include a vinyl group that reacts with the thiol group, and when the cellulose derivative includes a vinyl group, the polyvinyl acetal resin may include a thiol group that reacts with the vinyl group.

The cellulose derivative may be ethylcellulose 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 compound is a first 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 cellulose, and the polyvinyl acetal compound has a thiol group or a vinyl group. A second esterification reaction product is a dehydration condensation of a carboxy group of a carboxylic acid and a hydroxyl group of polyvinyl acetal, and 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 has the first esterification reaction product and the second ester It may also be a thiol-ene reaction product with a chemical reaction product.

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

The conductive powder may be nickel powder.

The number average particle diameter 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 diameter 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 laminated ceramic parts.

Furthermore, 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.

Further, in order to solve the above problems, the multilayer ceramic capacitor of the present invention 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. This is a multilayer ceramic capacitor formed using a multilayer ceramic capacitor.

The conductive paste of the present invention has excellent dispersibility of conductive powder, and has high surface smoothness in the dried film after application. Further, the electrode pattern of an electronic component such as a multilayer ceramic capacitor formed using the conductive paste of the present invention has excellent adhesion of the conductive paste even when forming a thin electrode.

FIG. 1 is a perspective view and a sectional view showing a multilayer ceramic capacitor according to this embodiment. It is a figure which evaluated the adhesiveness with the green sheet of the dry film which printed and dried the conductive paste.

Hereinafter, one embodiment of the conductive paste, electronic component, and multilayer ceramic capacitor of the present invention will be described.

[Conductive paste]
The conductive paste of this embodiment includes conductive powder, ceramic powder, dispersant, binder resin, and organic solvent. Each component will be explained in detail below.

(conductive powder)
The conductive powder is not particularly limited, and metal powder can be used, for example, one or more powders selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof. Among these, powders of Ni or alloys thereof are preferred from the viewpoints of conductivity, corrosion resistance, and cost. Examples of Ni alloys include alloys 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 alloys). can be used. The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Further, 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 binder removal treatment.

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

The number average particle diameter of the conductive powder is not particularly limited, and may be selected depending on the size of the electronic component to be used. The number average particle diameter of the conductive powder is preferably 0.5 μm or less, and more preferably 0.3 μm or less, for example, for multilayer ceramic capacitors whose films are becoming increasingly thin. If the average particle size exceeds 0.5 μm, the surface of the internal electrodes becomes extremely uneven, which may deteriorate the electrical characteristics of the capacitor, which is not preferable. Further, the lower limit of the average particle size of the conductive powder is not particularly limited, but is, for example, 0.03 μm or more. When the number average particle diameter is smaller than 0.03 μm, handling becomes extremely difficult.

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

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

(ceramic powder)
The ceramic powder is not particularly limited, and for example, in the case of a conductive paste for internal electrodes 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, preferably barium titanate (BaTiO ₃ ).

As the ceramic powder, a ceramic powder containing barium titanate as a main component and an oxide as a subcomponent may be used. Examples of oxides include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. Further, as the ceramic powder, for example, a perovskite-type oxide ferroelectric ceramic powder in which Ba atoms and Ti atoms of barium titanate (BaTiO ₃ ) are replaced with other atoms, such as Sn, Pb, and Zr, is used. It's okay.

In the conductive paste for 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 shrinkage mismatch 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, for example, ZnO, ferrite, PZT, BaO, _Al2O3 , _{Bi2O3 ,} R (rare earth element) _2O3 , _{TiO2 , Nd2O3 ,} etc. Examples include oxides. Note that one type of ceramic powder may be used, or two or more types of ceramic powder 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, preferably 0.01 μm or more and 0.3 μm or less. Since the number average particle size of the ceramic powder is within the above range, when used as an internal electrode paste, a sufficiently thin and uniform internal electrode can be formed. The number average particle diameter is a value obtained from observation with a scanning electron microscope (SEM), and the particle diameter of each particle is measured from an image observed with a SEM at a magnification of 50,000 times. This is the average value obtained.

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

(binder resin)
The binder resin used in the conductive paste of this embodiment includes a polymer compound in which cellulose, polyvinyl acetal, a cellulose compound and a polyvinyl acetal compound are bonded by sulfur atoms, and the sulfur atom contained in the polymer compound is The molar ratio of the cellulose to the total of the cellulose and the cellulose compound is from 0.3 to 1.7.

In other words, the binder resin used in the conductive paste of this embodiment contains a polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded together. The number average molecular weight (Mn) of this polymer compound is preferably 20,000 to 200,000, as calculated using standard polystyrene by gel permeation chromatography (GPC). The content of the polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded together is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 8 parts by mass or less, per 100 parts by mass of the conductive powder.

Since the molecules of the polymer compound of this embodiment include a part made of a cellulose compound and a part made of a polyvinyl acetal compound, the dry film obtained from the conductive paste of this embodiment has a smooth surface due to the cellulose compound. It can be provided with adhesive properties to green sheets due to the polyvinyl acetal compound. Furthermore, by providing the polymer compound with a structure of a cellulose compound and a polyvinyl acetal compound, which are not compatible with each other, in the same molecule, poor dispersion of the conductive paste can be solved.

Here, even if the molar ratio of the sulfur atoms contained in the polymer compound to the total of the cellulose and the cellulose compound is 0.5 to 2, conventional cellulose and polyvinyl acetal resin may be used in combination as a binder resin. However, if the molar ratio is 0.3 to 1.7, the surface roughness of the dried film and the density of the dried film of the conductive paste are better than that of the conductive paste. The molar ratio of the sulfur atoms contained in the polymer compound to the total of the cellulose and the cellulose polymer compound is 0.3 to 1.7, more preferably 0.5 to 1. It is 5.

The polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded that can be used in this embodiment will be described in more detail below.

Both cellulose and polyvinyl acetal have hydroxyl groups in their molecules. Cellulose-based compounds are chemically modified with reactive functional groups by introducing functional groups that can react with other compounds to form bonds into the hydroxyl groups of cellulose, while polyvinyl acetal-based polymer compounds have hydroxyl groups that contain other compounds. A polyvinyl acetal compound that can react with the cellulose compound to form a bond, has a functional group different from the functional group introduced into the cellulose compound, and is chemically modified with a reactive functional group is prepared. That is, the reactive functional group introduced into the cellulose compound is different from the reactive functional group introduced into the polyvinyl acetal compound. Note that, although the functional group introduced into the cellulose compound and the functional group introduced into the polyvinyl acetal compound react, it is difficult to react between the same functional groups. Here, the reason why it is difficult for the same functional groups to react is to avoid bonding between cellulose compounds and polyvinyl acetal compounds.

Then, when 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. To explain specifically, if a thiol group is introduced into cellulose to make a cellulose-based compound, and a vinyl group is introduced into a polyvinyl acetal resin to make a polyvinyl acetal-based compound, the thiol group and the vinyl group become the presence of a nucleophile. The double bond of the vinyl group and the sulfur atom of the thiol group bond together under conditions that generate radicals. As the polymer compound of the binder resin used in the conductive paste of the present embodiment, a polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded can be obtained by utilizing a bonding reaction between a thiol group and a vinyl group. Of course, a cellulose-based compound may be obtained by introducing a vinyl group into the hydroxyl group of cellulose, and a thiol group may be introduced into the hydroxyl group of a polyvinyl acetal resin to form a polyvinyl acetal-based compound.

That is, 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 vinyl group that reacts with the thiol group. It has a thiol group that reacts with.

The cellulose-based compound used as the binder resin of the conductive paste of the present embodiment is preferably a chemically modified polymer compound in which the compound is bonded to the hydroxyl group of cellulose, which is a natural polymer. Note that the chemical modification here is different from the chemical modification that introduces a functional group with reactivity as described above.

Bonding of the compound to the hydroxyl group of cellulose includes alkyl etherification, esterification, and the like. 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 protein, etc. Examples include pionate, cellulose acetate butyrate, nitrocellulose, and the like. Only one type of cellulose may be used, or two or more types of cellulose may be used in combination.

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

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

If the number average molecular weight of cellulose is less than 10,000, the viscosity of the conductive paste may become low, and if the number average molecular weight of cellulose exceeds 100,000, the viscosity of the conductive paste may become too high.

Not all of the hydroxyl groups in cellulose are chemically modified. The glucose rings constituting cellulose have three hydroxyl groups attached to them, and on average, 0.1 to 1 hydroxyl group per glucose ring of cellulose remains as a hydroxyl group and is not chemically modified. In this way, a reactive functional group is introduced into a hydroxyl group that has not been chemically modified.

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, and then acetalizing polyvinyl alcohol. . Specifically, examples include butyralized polyvinyl alcohol (polyvinyl butyral), formalized polyvinyl alcohol (polyvinyl formal), and the like.

Polyvinyl acetal may be a commercially available product, and various polyvinyl acetals with different butyralization degrees, formalization degrees, acetyl group weights, hydroxyl group weights, 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.

It is preferable that the polyvinyl acetal is soluble in an organic solvent. The polyvinyl acetal is more preferably polyvinyl butyral because of its high solubility in organic solvents.

The molecular weight of polyvinyl acetal affects the film strength and solution viscosity. Therefore, the number average molecular weight of 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 the polyvinyl acetal is less than 50,000, the solution viscosity will be extremely low, making it difficult to adjust the viscosity of the inorganic particle-containing composition (paste or slurry). There is a risk that the strength and adhesion of the resulting film will decrease.

Polyvinyl acetal has at least one hydroxyl group in one molecule. Generally, polyvinyl acetal has 20 to 40 mol% of hydroxy groups as vinyl alcohol units constituting the polymer. This hydroxyl group is chemically modified by introducing a reactive functional group.

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

A method for synthesizing the polymer compound used in this embodiment will be described.
To obtain a cellulose compound or a polyvinyl acetal 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 groups of cellulose or the hydroxyl groups 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 using a condensing agent, for example. Examples of the condensing agent include carbodiimide, diphenylphosphoric azide, and 1-hydroxybenzotriazole. Only one type of condensing agent may be used, or two or more types may be used in combination. Among these, carbodiimide is suitable because it has excellent versatility and reactivity, and allows the reaction to proceed under low temperature conditions and without being affected by moisture in the reaction environment.

Examples of carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide, N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide methiodade, etc. Can be mentioned. Among them, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferred from the viewpoint of availability. Further, when using carbodiimide, it is also preferable to use a base such as dimethylaminopyridine or triethylamine as a reaction accelerator in a range of 0.01 mol % to 10 mol % based on the carbodiimide.

The etherification reaction can be efficiently carried out by using an alkali metal hydroxide such as KOH or NaOH; or an alkali metal hydride such as NaH or KH as a reaction catalyst.

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 total of cellulose and cellulose-based compounds of 0.3 to 1.7. Therefore, 0.3 to 1.7 mol of a compound with a functional group that reacts with other compounds must be added per 1 mol of cellulose.

The reaction temperature for synthesizing the cellulose compound is preferably in the range of room temperature to 50°C.
The system in which the synthesis reaction of cellulose compounds has been completed consists of unreacted cellulose in which no functional group with a hydroxyl group is reactive with other compounds has been introduced, and cellulose compound in which one reactive functional group has been introduced. A mixture of cellulose-based compounds into which multiple reactive functional groups have been introduced. Although chemical modification is a matter of probability, cellulose compounds in which one hydroxyl group of cellulose is chemically modified are most common. After the synthesis of the cellulose compound is completed, the solvent may be removed by distillation.

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

The reaction temperature for chemical modification of the hydroxyl group of polyvinyl acetal is preferably in the range of room temperature to 50°C. After the synthesis of the polyvinyl acetal compound is completed, the solvent may be removed by distillation.

The polymer compound used in this embodiment can be obtained by dissolving a cellulose compound and a polyvinyl acetal compound in a solvent, adding a radical generator, and heating the resulting solution. and the thiol group provided on the other side react, and the cellulose-based compound and the polyvinyl acetal-based compound are bonded.

Alternatively, the cellulose compound and the polyvinyl acetal compound may be dissolved in a solvent, and a nucleophile such as a base such as an amine 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.

Solvents include conductive paste dihydroterpinyl acetate, isobornyl acetate, isobornyl propinate, isobornyl butyrate and isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate. Acetate solvents such as terpineol, terpene solvents such as dihydroterpineol can be used. If a solvent used for conductive paste is used as the solvent, a vehicle can be obtained in which the obtained polymer compound is dissolved in the solvent.

In this embodiment, in addition to polymer compounds in which a cellulose compound and a polyvinyl acetal compound are combined, cellulose resins such as methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and nitrocellulose, and butyral resins such as acrylic resins and polyvinyl acetal resins are used. It is also possible to add resins. The molecular weight of the resin that can be added in this way is about 20,000 to 200,000 in GCP.

The content of the binder resin is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less, based on the total amount of the conductive paste. When the content of the binder resin is within the above range, the conductivity and dispersibility are excellent.

For example, the cellulose derivative may be ethylcellulose 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 are dehydrated and condensed, and the polyvinyl acetal-based compound is , a second 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 polyvinyl acetal. When the first esterification reaction product includes a thiol group, the second esterification reaction product includes a vinyl group, and when the first esterification reaction product includes a vinyl group, the second esterification reaction product includes a vinyl group. The esterification reaction product may include 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 a carboxy group of 3-allyloxypropionic acid and a hydroxyl group of ethyl cellulose undergo dehydration condensation, 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.

(Organic solvent)
The organic solvent is not particularly limited, and any known organic solvent that can dissolve the binder resin can be used. Examples of organic solvents include dihydroterpinyl acetate, isobornyl acetate, isobornylpropinate, isobornyl butyrate and isobornyl isobutyrate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene Acetate solvents such as glycol monomethyl ether acetate and dipropylene glycol methyl ether acetate, terpene solvents such as terpineol and dihydroterpineol, hydrocarbon solvents such as tridecane, nonane, and cyclohexane, petroleum hydrocarbon solvents such as mineral spirit, etc. can be mentioned. In addition, one type of organic solvent may be used, or two or more types may be used.

The content of the organic solvent is preferably 40 parts by mass or more and 100 parts by mass or less, more preferably 65 parts by mass or more and 95 parts by mass or less, based on 100 parts by mass of the conductive powder. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

The content of the organic solvent is preferably 20% by mass or more and 60% by mass or less, more preferably 35% by mass or more and 55% by mass or less, based on the total amount of the conductive paste. When the content of the organic solvent is within the above range, the conductivity and dispersibility are excellent.

(dispersant)
The conductive paste of this embodiment contains a polymer dispersant. The role of polymeric dispersants is to adsorb to the surface of inorganic powders (conductive powders and ceramic powders), suppress agglomeration of inorganic powders, improve wettability with organic vehicles, and disperse within conductive paste. It is to do something.

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

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 or more and 100,000 or less, more preferably 5,000 or more and 70,000 or less, and even more preferably 10,000 or more and 60,000 or less. When the mass average molecular weight of the polymer dispersant is 1000 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 organic vehicles and organic solvents may decrease, particles such as conductive powders and ceramic powders may aggregate, and dispersibility and storage stability may decrease. It may cause.

Such a polymeric dispersant has a carboxy group or a carboxylic acid anhydride group as a functional group in the main chain. It is desirable for the anionic polymer dispersant to further include an oxyethylene group in the graft chain in view of adsorption with the inorganic powder.

The anionic polymer dispersant can contain one or more types. That is, a plurality of types of polymer dispersants can be included depending on the length of the main chain, the length of the graft chain, the presence or absence of the graft chain, etc. The content of the anionic polymer dispersant in the conductive paste can be appropriately selected in consideration of the viscosity, viscosity, long-term storage stability, etc. of the conductive paste, and may be included within a range that does not impede the effects of the present invention.

For example, the amount of anionic polymer dispersant added to 100 parts by mass of the conductive metal powder is preferably 0.01 to 5.00 parts by mass, more preferably 0.20 to 2.00 parts by mass. More preferred. If the amount of the dispersant added is less than 0.01 parts by mass, it tends to be difficult to obtain sufficient dispersibility. On the other hand, if the amount of the dispersant added exceeds 5.00 parts by mass, problems such as poor drying properties and decreased dry film density will occur.

Such anionic polymer dispersants are copolymers such as maleic anhydride and polyoxyalkylene with an allyl group at the end, or copolymers of acrylic acid and polyoxyalkylene with an allyl group at the end. Copolymers of these compounds and copolymers of styrene are known. Examples of the structural formulas of such anionic polymer dispersants include the following formulas (1) to (3) shown in [Chemical Formula 1] to [Chemical Formula 3]. For example, in formulas (1) to (3), R is an alkyl group, m is an integer of 2 to 30, and n is an integer of 10 to 30. Further, R is preferably an alkyl group having 5 to 30 carbon atoms, more preferably an alkyl group having 8 to 25 carbon atoms, and particularly preferably an alkyl group having 10 to 20 carbon atoms.

The conductive paste of this embodiment can contain a dispersant in addition to the anionic polymer dispersant. For example, dispersants (surfactants) include acid-based dispersants containing higher fatty acids, phosphoric acid, polymeric surfactants, etc., cationic dispersants other than acid-based dispersants, nonionic dispersants, amphoteric surfactants, etc. It may also contain a polymeric dispersant and a polymeric dispersant.

Further, the content of the dispersant in the conductive paste can be appropriately selected in consideration of the viscosity, viscosity, long-term storage stability, etc. of the conductive paste, and may be included within a range that does not impede the effects of the present invention.

Furthermore, for both anionic polymer dispersants and other dispersants, the mass average molecular weight of the dispersant is preferably 200 to 100,000. More preferably 300 to 30,000. If the mass average molecular weight is less than 200, the dispersibility and storage stability of the particles may decrease. Usually, a paste with excellent dispersibility can be obtained by adsorbing a dispersant to the particle surface to form an adsorption layer of the dispersant and imparting electrostatic repulsion or steric repulsion to the particles. However, as time passes, it is thought that particles collide with each other, overcoming the repulsive force of the adsorption layer and causing the particles to aggregate, so the mass average molecular weight is preferably 200 or more. On the other hand, if the mass average molecular weight is greater than 100,000, the compatibility with organic vehicles and organic solvents may decrease, particles may aggregate with each other, and dispersibility and storage stability may decrease. Further, a problem arises in that the viscosity of the paste becomes high.

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

(Method for manufacturing conductive paste)
The method for manufacturing the conductive paste of this embodiment is not particularly limited, and conventionally known methods can be used. The conductive paste can be produced, for example, by preparing the above-mentioned components and stirring and kneading them using a three-roll mill, a ball mill, a mixer, or the like. At this time, if a dispersant is applied to the surface of the conductive powder in advance, the conductive powder will be sufficiently loosened without agglomerating, and the dispersant will be spread over the surface, making it easier to obtain a uniform conductive paste. In addition, the binder resin is dissolved in an organic solvent for a vehicle to prepare an organic vehicle, a conductive powder, a ceramic powder, an organic vehicle, and a dispersant are added to the organic solvent for a paste, and the mixture is stirred and kneaded with a mixer. A conductive paste may also be prepared.

Further, as the organic solvent for the vehicle, 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. Further, the content of the organic solvent for the vehicle is preferably 10% by mass or more and 40% by mass or less based on the entire amount of the conductive paste.

The surface smoothness of the dry 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 dry film is evaluated by the arithmetic mean height Sa, it is preferable that the value is 0.10 μm or less.

[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.

Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. In the drawings, the drawings may be expressed schematically or with a changed scale, as appropriate. Further, the positions and directions of members will be explained with reference to the XYZ orthogonal coordinate system shown in FIG. 1 and the like as appropriate. In this XYZ orthogonal coordinate system, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction (up and down direction).

1A and 1B are a perspective view and a side sectional view showing 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, which is an unfired ceramic sheet made of dielectric material, is prepared. This green sheet is made of a dielectric layer paste obtained by adding an organic binder such as polyvinyl butyral and a solvent such as terpineol to a predetermined ceramic raw material powder such as barium titanate. Examples include those obtained by applying a sheet onto a film and drying it to remove the solvent. Note that the thickness of the dielectric layer made of green sheets is not particularly limited, but from the viewpoint of the demand for miniaturization of multilayer ceramic capacitors, it is preferably 0.05 μm or more and 3 μm or less.

Next, a plurality of green sheets are prepared in which the above-mentioned conductive paste is printed (coated) on one side of the green sheet by a known method such as screen printing and dried to form a dry film. Note that the thickness of the conductive paste (dry film) after printing is preferably such that the thickness of the dry film after drying is 1 μm or less, from the viewpoint of the demand for thinning of the internal electrode layer 11.

Next, the green sheet is peeled off from the support film, and the dielectric layer made of the green sheet and the dry film formed on one side of the green sheet are laminated in an alternating manner, and then the laminate is heated and pressurized. get. Note that a configuration may be adopted in which protective green sheets to which no conductive paste is applied are further disposed on both sides of the laminate.

Next, after cutting the laminate into a predetermined size to form a green chip, the green chip is subjected to binder removal treatment and fired in a reducing atmosphere to produce the ceramic laminate 10. Note that the atmosphere in the binder removal treatment is preferably air or N2 gas atmosphere. The temperature when performing the binder removal treatment is, for example, 200°C or more and 400°C or less. Further, it is preferable that the holding time at the above temperature during the binder removal treatment is 0.5 hours or more and 24 hours or less. Further, the firing is performed in a reducing atmosphere to suppress oxidation of the metal used for the internal electrode layer, and the temperature when firing the laminate is, for example, 1000°C or more and 1350°C or less, and the firing is The temperature is maintained for a period of, for example, 0.5 hours or more and 8 hours or less.

By firing the green chip, the organic binder in the green sheet is completely removed, and the ceramic raw material powder is fired to form the ceramic dielectric layer 12. Further, the organic vehicle in the dried film is removed, and the nickel powder or the alloy powder mainly composed of nickel is sintered or melted and integrated to form the internal electrode layer 11, thereby forming the dielectric layer. A multilayer ceramic fired body is formed in which a plurality of internal electrode layers 12 and internal electrode layers 11 are alternately stacked. Note that from the viewpoint of increasing reliability by incorporating oxygen into the dielectric layer and suppressing re-oxidation of the internal electrodes, the fired multilayer ceramic fired body may be subjected to an annealing treatment.

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

Hereinafter, the present invention will be explained in detail based on Examples and Comparative Examples, but the present invention is not limited by the Examples in any way.

[Materials used]
(conductive powder)
As the conductive powder, Ni powder (number average particle diameter 0.2 μm by SEM measurement) was used.

(ceramic powder)
As the ceramic powder, barium titanate (BaTiO ₃ ; number average particle diameter 0.05 μm as measured by SEM) was used.

(binder resin)
The binder resin was synthesized as follows.

(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 per glucose ring: 0.48) was prepared and dried.

100 parts by mass of the dried ethyl cellulose was dissolved in 900 parts by mass of ethyl acetate to obtain a solution. To the resulting solution, 0.09 parts by mass of 3-allyloxypropionic acid, which corresponds to an average amount of 0.5 vinyl groups introduced per molecule of ethylcellulose, 0.10 parts by mass of diisopropylcarbodiimide as a condensing agent, 0.002 parts by mass of dimethylaminopyridine as a reaction accelerator was added, and the mixture was stirred at a temperature of 40° C. for 5 hours to carry out a reaction. Thereafter, ethyl acetate was removed to obtain a solid cellulose compound (1a) in which a vinyl group was introduced into ethyl cellulose.

When a part of the obtained solid was analyzed by FT-IR and 1H-NMR, it was confirmed that an ester bond was formed, and that the same molar amount of vinyl groups as the charged 3-allyloxypropionic acid was introduced into the ethylcellulose. It was confirmed that

Note that the cellulose-based compound (1a) contains a compound in which a vinyl group is introduced into ethylcellulose, as well as unreacted ethylcellulose, but in the examples, a mixture of these is referred to as the cellulose-based compound (1a).

(Synthesis of polyvinyl butyral compound (1b) having a 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 weight: about 22 mol %) was prepared and dried. 100 parts by mass of dried polyvinyl butyral was dissolved in 900 parts by mass of ethyl acetate. To the resulting solution, 0.10 parts by mass of 3-mercaptopropionic acid, which corresponds to the amount of introduction of an average of 0.5 thiol groups per molecule of polyvinyl butyral, 0.12 parts by mass of diisopropylcarbodiimide as a condensing agent, 0.003 parts by mass of dimethylaminopyridine as a reaction accelerator was added, and the mixture was stirred at a temperature of 40° C. for 5 hours to carry out a reaction. Thereafter, by removing ethyl acetate, a polyvinyl butyral compound (1b) in which a thiol group was introduced into polyvinyl butyral was obtained as a solid.

When a part of the obtained solid was analyzed by FT-IR and 1H-NMR, it was confirmed that an ester bond was formed, and that the same molar amount of thiol group as the charged 3-mercaptopropionic acid was introduced into the polyvinyl butyral. It was confirmed that

Note that the polyvinyl butyral compound (1b) contains a mixture of unreacted polyvinyl butyral as well as a compound in which a thiol group has been introduced into polyvinyl butyral. ).

(Synthesis of polymer compound 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 dihydroterpineol as a solvent, and this solution was transferred to a glass flask reaction vessel and replaced with nitrogen. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added to the solution as a radical generator, and the reaction was carried out at 80° C. for 3 hours with stirring to obtain organic vehicle 1 containing polymer compound 1. Here, the cellulose compound (1a) and the polyvinyl butyral compound (1b) have the same mol number, and since an average of 0.5 thiol groups were introduced into one molecule of polyvinyl butyral as described above, the polymer The molar ratio of the sulfur atoms contained in Compound 1 to the total of cellulose and cellulose compound is 0.5. Organic vehicle 1 contains 13.5% by mass of polymer compound 1. Note that the polymer compound 1 here includes a polymer compound in which a cellulose compound (1a) and a polyvinyl butyral compound (1b) are combined, unreacted ethyl cellulose, and unreacted polyvinyl butyral. In the example, a mixture of these is referred to as polymer compound 1.

Furthermore, when the produced polymer compound 1 was analyzed by FT-IR and 1H-NMR, an -S- bond was confirmed, and the desired structure was obtained. Furthermore, the number average molecular weight (Mn: standard polystyrene equivalent value determined by GPC) of Polymer Compound 1 was measured.

Table 1 shows the characteristics of the cellulose-based compound (1a) and polyvinyl acetal-based compound (1b) used in polymer compound 1.

[Example 1]
47% by mass of Ni powder, 4.7% by mass of ceramic powder, 26.67% by mass of organic vehicle 1, anionic polymer dispersant of polymeric polycarboxylic acid having the structural formula shown in formula (1) above (R is carbon 0.4% by mass of 5 to 30 alkyl groups, mass average molecular weight 40,000), and 21.23% by mass of the remaining organic solvent (dihydroterpineol), for a total of 100% by mass, and these materials were mixed. A conductive paste was prepared by mixing. The produced conductive paste was printed and dried as follows, and the surface roughness of the dried film and the adhesion to the green sheet were evaluated. The evaluation results are shown in Table 2 and FIG. 2.

[Evaluation method]
(Dispersibility: surface roughness of dry film and adhesion to green sheet)
<Surface roughness>
By screen printing the prepared conductive paste on a 2.54 cm (1 inch) square heat-resistant tempered glass and drying it in the air at 120°C for 1 hour, a 20 mm square dry film with a film thickness of 1 to 3 μm was created. did. If the conductive paste has good dispersibility, the surface of the dried film will be smooth. If the dispersibility is poor, agglomeration occurs within the conductive paste, the surface of the dried film becomes rough, and the surface smoothness decreases. Therefore, the surface roughness Sa (arithmetic mean height) of the produced dry film was measured based on the ISO 25178 standard using a laser microscope (VK-X120 manufactured by Keyence Corporation). The smaller the value of the surface roughness Sa (arithmetic mean height), the smoother the surface of the dried film.
In addition, the obtained dried film was observed using SEM.

<Adhesion between dry film and green sheet>
The prepared conductive paste was printed on a 2.54 cm (1 inch) square BaTiO ₃ dielectric green sheet in a 2 cm square pattern by adjusting the printer so that the film thickness after printing was 3.6 μm. After printing, it was dried at 120° C. for 20 minutes to form a dry film of conductive paste on the surface of the green sheet. Next, the dried conductive paste film was covered with a BaTiO ₃ dielectric green sheet, and the dried conductive paste film and the BaTiO ₃ dielectric green sheet were thermocompression bonded using a hydrostatic press at 80°C and 98 MPa to create a laminate. . The adhesion between the dried conductive paste film and the BaTiO ₃ dielectric green sheet was evaluated by measuring the peeling force between the dried conductive paste film and the BaTiO ₃ dielectric green sheet of the obtained laminate. . This adhesion was measured using a thin film adhesion strength measuring device (Romulus, manufactured by Phototechnica). To explain in detail the process of adhesion evaluation using a thin film adhesion strength measuring machine, an aluminum stud pin coated with epoxy adhesive is glued vertically to the center of the laminate, and the stud pin is vertically Prepare a bonded sample for adhesion evaluation, and evaluate the adhesion between the dry conductive paste film and the BaTiO ₃ dielectric green sheet by pulling the stud pin of the sample off the surface of the laminate. did. The evaluation results of adhesion are shown as the results of a relative evaluation with the adhesion strength of Comparative Example 1, which will be described later, as 100.

[Comparative example 1]
A conductive paste was prepared and evaluated in the same manner as in Example 1, except that an anionic dispersant of an amide compound of an amino acid and a fatty acid (hereinafter referred to as dispersant B, molecular weight 353) was used. The results are shown in Table 2 and Figure 2.

[Evaluation results]
As shown in Table 2, the dry film formed using the conductive paste of Example 1 had a surface roughness Sa (arithmetic mean height) of 0.06 μm, which was lower than that of Comparative Example 1. Furthermore, as shown in the SEM photograph in Table 2, it can be seen that the film has fewer irregularities than Comparative Example 1.

On the other hand, the dry film formed using the conductive paste of Comparative Example 1 had a surface roughness Sa of 0.9 μm, and the surface was rougher than that of Example 1. Furthermore, as shown in the SEM photograph in Table 2, the film had larger irregularities compared to Example 1.

Furthermore, according to FIG. 2, it can be seen that the dried film of Example 1, which has a superior surface roughness Sa, has superior adhesion to the BaTiO ₃ dielectric green sheet than the dried film of Comparative Example 1.

In the conductive paste according to this embodiment using finely divided conductive powder or ceramic powder, it is possible to provide a conductive paste that has a smooth dry film and has excellent adhesion. Therefore, it can be particularly suitably used as a raw material for internal electrodes of multilayer ceramic capacitors, which are chip components (electronic components) of electronic devices such as mobile phones and digital devices.

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)

Contains conductive powder, ceramic powder, dispersant, binder resin, and organic solvent,
The binder resin includes a polymer compound in which cellulose, polyvinyl acetal, a cellulose compound and a polyvinyl acetal compound are bonded via a sulfur atom,
The molar ratio of the sulfur atoms contained in the polymer compound to the total of the cellulose and the cellulose compound is 0.3 to 1.7,
A conductive paste, wherein the dispersant is an anionic polymer compound. The conductive paste according to claim 1, wherein the dispersant includes a carboxy group or a carboxylic acid anhydride group. The cellulose 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 includes a thiol group, the polyvinyl acetal resin includes a vinyl group that reacts with the thiol group,
The conductive paste according to claim 1 or 2, wherein when the cellulose derivative includes a vinyl group, the polyvinyl acetal resin includes a thiol group that reacts with the vinyl group. The cellulose derivative is ethylcellulose having a thiol group or a vinyl group,
The conductive paste according to claim 3, wherein the polyvinyl acetal resin is polyvinyl butyral having a thiol group or a vinyl group. The cellulose-based compound is 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 are dehydrated and condensed,
The polyvinyl acetal compound is 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 the polyvinyl acetal undergo dehydration condensation,
When the first esterification reaction product includes a thiol group, the second esterification reaction product includes a vinyl group,
When the first esterification reaction product includes a vinyl group, the second esterification reaction product includes a thiol group,
The conductive paste according to claim 1, wherein the polymer compound is a thiol-ene reaction product of the first esterification reaction product and the second esterification reaction product. 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,
The conductive paste 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. The conductive paste according to claim 1 or 2, wherein the conductive powder is nickel powder. The conductive paste according to claim 1, wherein the conductive powder has a number average particle diameter of 0.05 μm or more and 1.0 μm or less. The conductive paste of claim 1, wherein the ceramic powder includes barium titanate. The conductive paste according to claim 1, wherein the ceramic powder has a number average particle diameter of 0.01 μm or more and 0.5 μm or less. The conductive paste according to claim 1, wherein the content of the ceramic powder is 1% by mass or more and 20% by mass or less. The conductive paste according to claim 1, which is used for internal electrodes of laminated ceramic parts. An electronic component formed using the conductive paste according to claim 1. It has at least a laminate including a dielectric layer and an internal electrode layer,
A multilayer ceramic capacitor, wherein the internal electrode layer is formed using the conductive paste according to claim 1.

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