Electrically conductive paste, electronic component, and multilayer ceramic capacitor

Abstract

Provided are: an electrically conductive paste in which there are used an electrically conductive powder and a ceramic powder that are refined in order to reduce the size and thickness of a multilayer ceramic electronic component, the electrically conductive paste making it possible to form an internal electrode layer that has a smooth dry film and exhibits exceptional adhesive properties; 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 a cellulose resin, one or more resins selected from polyvinyl acetal resins, and a polymer compound in which a cellulose-based compound and a polyvinyl-acetal-based compound are bonded by sulfur atoms. In the polymer compound, the molar ratio of the sulfur atoms to the cellulose-based compound is 0.3–1.7. The electrically conductive paste contains 20 mass% or more of the polymer compound with respect to the total mass of the cellulose resin, the polyvinyl acetal resin, and the polymer compound.

Description

Conductive paste, electronic components and multilayer ceramic capacitors

[0001] The present invention relates to a conductive paste, an electronic component, and a multilayer ceramic capacitor.

[0002] As electronic devices such as mobile phones and digital devices become smaller and more powerful, there is a demand for smaller and higher-capacity electronic components, including multilayer ceramic capacitors. Multilayer ceramic capacitors have a structure in which multiple dielectric layers and multiple internal electrode layers are alternately stacked, and by reducing the thickness of these dielectric layers and internal electrode layers, it is possible to achieve smaller size and higher capacity.

[0003] For example, a multilayer ceramic capacitor is manufactured as follows: First, barium titanate (BaTiO ３ A conductive paste for internal electrodes is printed (applied) in a predetermined electrode pattern onto the surface of a green sheet containing a dielectric powder such as BT (hereinafter sometimes referred to as "BT") and a binder resin such as polyvinyl acetal resin (PVA), and then dried to form a dry film. Next, the dried film and the green sheet are alternately stacked and heat-pressed to form an integrated laminate. This laminate is cut, subjected to an organic binder removal treatment in an oxidizing or inert atmosphere, and then fired to obtain fired chips. Next, a paste for external electrodes is applied to both ends of the fired chip, and after firing, the surfaces of the external electrodes are nickel-plated or the like to obtain multilayer ceramic capacitors (MLCCs).

[0004] In recent years, there has been a demand for MLCCs to be even smaller and have larger capacities, and for example, for internal electrodes using nickel or the like, efforts have been made to make the electrode films thinner, with excellent density and continuity, and for ceramic dielectric materials and dielectric layers using such materials, efforts have been made to make the dielectric layers thinner and with higher dielectric constants, and dielectric layers with thicknesses of 1.0 μm or less have already been put into practical use. It is also desirable for the electrode films to have thicknesses of 1.0 μm or less.

[0005] One of the required characteristics for miniaturizing and increasing the capacity of MLCCs is the suppression of a decrease in insulation resistance under high temperatures and high voltages, i.e., high reliability. The decrease in insulation resistance is said to be caused by the occurrence of unevenness on the surface of the Ni electrode layer sandwiching the dielectric layer during the sintering process, which causes the electric field to concentrate on the uneven surfaces. During the sintering process, the Ni powder sinters and undergoes a densification process, forming the Ni electrode layer. However, because fine Ni powder sinters quickly, the electrode is prone to breakage and spheroidization. As a result, the effective electrode area of ​​the Ni electrode layer decreases, reducing the capacity of the MLCC, and the unevenness on the surface of the Ni electrode layer leads to a decrease in the insulation resistance of the MLCC.

[0006] As MLCCs become thinner, the adhesion between the green sheets and the internal electrode layers decreases, leading to problems such as frequent peeling and misalignment during lamination due to insufficient adhesion during lamination. To address this issue, internal electrode pastes containing plasticizers are often used. However, adding plasticizers can significantly reduce the elastic modulus of the printed film (a reduced elastic modulus makes the printed film softer and more susceptible to deformation). Even if adhesion is improved, this can lead to significant problems such as poor cutting. Furthermore, adding plasticizers increases the amount of gas generated during the organic binder removal process, which can cause cracks.

[0007] When ceramic green sheets are stacked and pressed in the thickness direction, weak adhesion between the green sheets can cause poor adhesion between the green sheets. This poor adhesion can lead to short circuits in multilayer ceramic capacitors, for example. In particular, the need for multilayer MLCCs requires the use of fine-particle dielectric powder to reduce the thickness of each dielectric layer and increase the number of layers, making it desirable to improve the poor adhesion. Weak adhesion between sheets can cause structural defects such as delamination, voids, and cracks during firing, which reduces the yield of MLCCs.

[0008] To improve such poor adhesion, the following measures 1) and 2) can be considered. 1) Increasing the amount of binder or tackifier is conceivable, but simply increasing the amount does not significantly improve adhesion. Conversely, in this case, the amount of organic matter, such as organic binder and tackifier, added increases, which makes it difficult to remove the organic binder. Even after the organic binder removal process, the remaining organic matter (residual carbon) may cause structural defects in the MLCC during the firing process. 2) When stacking multiple ceramic green sheets with conductive paste films, smoothing the surface of the conductive paste coating increases the contact area between the paste film and the ceramic green sheets, thereby improving adhesion.

[0009] While the goal of improving adhesion between the internal electrodes and green sheets is to prevent cracking, using butyral resin as the resin can prevent electrode peeling when the laminate is cut. Cellulose-based resins such as ethyl cellulose have been primarily used as organic binders. While cellulose-based resins are highly compatible with various solvents and are effective in imparting the desired rheological properties to conductive pastes, they lack significant thermoplasticity, resulting in the dry film of the conductive paste maintaining little adhesion to the top surface during thermocompression bonding. As a result, no conductive paste for multilayer ceramic capacitor internal electrodes has yet been developed that can further improve the thermocompression bonding between the internal electrodes of green sheets screen-printed with conductive paste and the green sheet above them, prevent electrode misalignment within the chip, improve electrode alignment, and prevent chip cracking and peeling, thereby enabling high stacking density.

[0010] Therefore, the internal electrode paste can contain an organic resin, and the organic binder resin is preferably a mixed system of ethyl cellulose (EC) and polyvinyl butyral (PVB) resin, which is a type of polyvinyl acetal (PVA) resin.

[0011] Ethyl cellulose (EC) can be suitably used as a binder for the internal electrode paste due to its good solubility in solvents, printability, combustion decomposition properties, etc. Furthermore, by using polyvinyl butyral (PVB) resin, which is a type of polyvinyl acetal (PVA) resin used in green sheets, together as an organic binder resin, it is possible to increase the adhesive strength between the green sheet and the dried film of the internal electrode paste.

[0012] Patent Documents 1 and 2 disclose a conductive paste containing a cellulose-based resin and a polyvinyl butyral resin as a binder resin, and disclose that the paste improves adhesion to ceramic green sheets.

[0013] 5299904 publication 5224722 publication

[0014] However, when two different organic binder resins are mixed, they are generally incompatible (immiscible). In the case of an immiscible system, the two organic binder resins are essentially not soluble in each other and exist independently, so not only are they unable to exhibit the expected performance, but their functionality is often significantly reduced.

[0015] When the resin becomes less soluble in the solvent, the smoothness of the dried paste film deteriorates. For example, when EC and PVB are mixed, a typical "sea-island structure" is observed, and phase separation is confirmed. As a result, the distribution of inorganic particles (Ni, BT) in the dried film becomes non-uniform. In this way, the combination of organic materials in the paste composition affects the dispersibility of inorganic particles (Ni, BT) in the dried film.

[0016] By making polymers that are normally immiscible compatible with each other, the properties of both can be combined, the interface between the different polymers can be stabilized, and a uniform and stable dispersion state can be achieved.

[0017] Furthermore, the conductive pastes disclosed in Patent Documents 1 and 2 contain polyvinyl butyral resin, which improves the adhesion between the dried film and the green sheet. However, these techniques use a combination of cellulose-based resin and polyvinyl butyral resin, which results in poor compatibility between the two resins, resulting in insufficient dispersion of the conductive powder and ceramic powder in the paste, and in insufficient density and smoothness of the dried film of the conductive paste. Such dried film properties are not sufficient to meet the increasing capacitance of multilayer ceramic capacitors in recent years.

[0018] In view of the above circumstances, an object of the present invention is to provide a conductive paste using a finely divided conductive powder or ceramic powder for reducing the size and thickness of a multilayer ceramic electronic component, which is capable of forming an internal electrode layer having a smooth dried film and excellent adhesion, an electronic component, and a multilayer ceramic capacitor.

[0019] In order to solve the above problems, the conductive paste of the present invention comprises a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, wherein the binder resin comprises one or more resins selected from a cellulose resin and a polyvinyl acetal resin, and a polymer compound in which a cellulose compound and a polyvinyl acetal compound are bonded together via a sulfur atom, wherein the molar ratio of the sulfur atoms to the cellulose compound in the polymer compound is 0.3 to 1.7, and the polymer compound accounts for 20 mass% or more of the total mass of the cellulose resin, the polyvinyl acetal resin, and the polymer compound.

[0020] 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.

[0021] 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.

[0022] The cellulose-based compound may be 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 with a hydroxyl group of cellulose; the polyvinyl acetal-based compound may be 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 with a hydroxyl group of polyvinyl acetal; if the first esterification reaction product has a thiol group, the second esterification reaction product may have a vinyl group; if the first esterification reaction product has a vinyl group, the second esterification reaction product may have 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.

[0023] The first esterification reaction product may be an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-allyloxypropionic acid and a hydroxy group of ethyl cellulose, and the second esterification reaction product may be an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-mercaptopropionic acid and a hydroxy group of polyvinyl butyral.

[0024] The cellulose resin may be an ethyl cellulose resin, and the polyvinyl acetal resin may be a polyvinyl butyral resin.

[0025] The conductive powder may be nickel powder.

[0026] The number average particle size of the conductive powder may be 0.05 μm or more and 1.0 μm or less.

[0027] The ceramic powder may include barium titanate.

[0028] The ceramic powder may have a number average particle size of 0.01 μm or more and 0.5 μm or less.

[0029] The content of the ceramic powder may be 1% by mass or more and 20% by mass or less.

[0030] The conductive paste of the present invention may be used for internal electrodes of multilayer ceramic components.

[0031] In order to solve the above-mentioned problems, the electronic component of the present invention is an electronic component formed using the conductive paste of the present invention.

[0032] In order to solve the above-mentioned problems, the multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor having at least a laminate in which dielectric layers and internal electrode layers are laminated, and the internal electrode layers are formed using the conductive paste of the present invention.

[0033] The present invention can provide a conductive paste using a finely divided conductive powder or ceramic powder for reducing the size and thickness of a multilayer ceramic electronic component, which can form an internal electrode layer having a smooth dry film and excellent adhesion, an electronic component, and a multilayer ceramic capacitor.

[0034] 1A and 1B are perspective and cross-sectional views of the multilayer ceramic capacitor according to the present embodiment.

[0035] Hereinafter, an embodiment of the conductive paste, electronic component, and multilayer ceramic capacitor of the present invention will be described.

[0036] [Conductive Paste] The conductive paste of this embodiment contains a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent. Each component will be described in detail below.

[0037] <Conductive Powder> The conductive powder is not particularly limited, and metal powders can be used. For example, powders of one or more elements selected from Ni, Pd, Pt, Au, Ag, Cu, and alloys thereof can be used. Among these, powders of Ni or its alloys are preferred from the viewpoints of conductivity, corrosion resistance, and cost. Examples of Ni alloys that can be used include alloys of Ni with at least one element selected from the group consisting of Mn, Cr, Co, Al, Fe, Cu, Zn, Ag, Au, Pt, and Pd (Ni alloys). The Ni content in the Ni alloy is, for example, 50% by mass or more, preferably 80% by mass or more. Furthermore, the Ni powder may contain several hundred ppm of S to suppress rapid gas generation due to partial thermal decomposition of the binder resin during binder removal treatment.

[0038] The method for producing the conductive powder is not particularly limited, and examples thereof include 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, and a wet method in which a raw material metal salt is reduced in an aqueous solution.

[0039] 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, for example, 0.05 μm or more and 1.0 μm or less. For example, for multilayer ceramic capacitors, which are becoming thinner, the number average particle diameter of the conductive powder is preferably 0.5 μm or less, more preferably 0.3 μm or less. A number average particle diameter exceeding 0.5 μm is undesirable because it can cause severe unevenness on the internal electrode surface and degrade the electrical characteristics of the capacitor. 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. A number average particle diameter smaller than 0.03 μm can make handling extremely difficult.

[0040] The number average particle size of the conductive powder is a value determined by observation using 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.

[0041] 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 less than 60% by mass, based on the total amount of the conductive paste. When the content of the conductive powder is preferably 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.

[0042] <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-type oxides containing Ba and Ti, and preferably barium titanate (BaTiO ３ BT).

[0043] The ceramic powder may be a ceramic powder containing barium titanate as a main component and an oxide as a secondary component. Examples of the oxide include oxides of Mn, Cr, Si, Ca, Ba, Mg, V, W, Ta, Nb, and one or more rare earth elements. Examples of the ceramic powder include barium titanate (BaTiO ３ Alternatively, a ceramic powder of a perovskite-type oxide ferroelectric may be used in which the Ba atoms or Ti atoms of the above-mentioned alloy are substituted with other atoms such as Sn, Pb, or Zr.

[0044] In the conductive paste for the internal electrodes, powder of the same composition as the dielectric ceramic powder constituting the green sheets of the multilayer ceramic capacitor may be used as the ceramic powder. This suppresses the occurrence of cracks due to a mismatch in shrinkage at the interface between the dielectric layer and the internal electrode layer during the sintering process. In addition to the above, examples of such ceramic powders include ZnO, ferrite, PZT, BaO, and Al. ２ O ３ , Bi ２ O ３ , R (rare earth element) ２ O ３ , TiO ２ , Nd ２ O ３The ceramic powder may be one type or two or more types.

[0045] 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. When the ceramic powder has a number average particle diameter of 0.01 μm or more and 0.5 μm or less, when used as an internal electrode paste, a sufficiently fine, thin, and uniform internal electrode can be formed. 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 a plurality of particles in an image observed with the SEM at a magnification of 50,000 times.

[0046] 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, relative to 100 parts by mass of the conductive powder. When the content of the ceramic powder is 1 part by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the conductive powder, the conductivity and dispersibility are excellent.

[0047] 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 ceramic powder is 1% by mass or more and 20% by mass or less, based on the total amount of the conductive paste, the conductive paste has excellent conductivity and dispersibility.

[0048] <Binder Resin> The binder resin used in the conductive paste of the present embodiment includes a cellulose resin, one or more resins selected from a polyvinyl acetal resin, and a polymer compound in which a cellulose-based compound and a polyvinyl acetal compound are bonded together via a sulfur atom, wherein the polymer compound has a molar ratio of sulfur atoms to the cellulose-based compound of 0.3 to 1.7, and the polymer compound accounts for 20 mass% or more of the total mass of the cellulose resin, the polyvinyl acetal resin, and the polymer compound.

[0049] That is, the binder resin used in the conductive paste of this embodiment includes a polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded. The mass-average molecular weight (Mw) of this polymer compound, as measured by gel permeation chromatography (GPC) using standard polystyrene, is preferably 20,000 to 200,000. If the number-average molecular weight of the polymer compound is less than 20,000, the viscosity of the conductive paste prepared therefrom may be extremely low, making it difficult to adjust the viscosity to an appropriate level for the conductive paste. Furthermore, if the mass-average molecular weight of the polymer compound exceeds 200,000, the viscosity of the conductive paste prepared therefrom may be extremely high, making it difficult to adjust the viscosity to an appropriate level for the conductive paste. In order to adjust the viscosity to an appropriate level, it may be necessary to reduce the content of the conductive powder or ceramic powder below the appropriate level.

[0050] 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 in the range of 0.5% by mass or more and 10% by mass or less, the conductivity of the internal electrode layer and the dispersibility of the conductive powder and the ceramic powder in the conductive paste are excellent.

[0051] The content of the polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded 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.

[0052] The polymer compound molecules of this embodiment contain both cellulose-based and polyvinyl acetal-based compounds, allowing the dried film obtained from the conductive paste of this embodiment to have the surface smoothness provided by the cellulose-based compound and the adhesion to the green sheet provided by the polyvinyl acetal-based compound. Furthermore, the polymer compound contains the structures of the cellulose-based compound and the polyvinyl acetal-based compound, which are incompatible with each other, within the same molecule, thereby eliminating poor dispersion of the conductive paste.

[0053] Here, even if the molar ratio of the sulfur atoms to the cellulose-based compound in the polymer 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 a polyvinyl acetal resin in combination as a binder resin, but 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 even superior. In the polymer compound, the molar ratio of the sulfur atoms to the cellulose-based compound is 0.3 to 1.7 (i.e., in the polymer compound, the cellulose-based compound:sulfur atom=1.0:0.3 to 1.7), and more preferably the molar ratio is 0.5 to 1.5 (i.e., in the polymer compound, the cellulose-based compound:sulfur atom=1.0:0.5 to 1.5).

[0054] (Polymer Compound) The polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded, which can be used in this embodiment, will be described in more detail.

[0055] 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 into the hydroxyl groups of cellulose, thereby preparing a cellulose-based compound chemically modified with the reactive functional group. Furthermore, a functional group capable of reacting with other compounds to form bonds and different from the functional group introduced into the cellulose-based compound is introduced into the hydroxyl groups of a polyvinyl acetal-based polymer compound, thereby preparing a polyvinyl acetal-based compound chemically modified with the reactive functional group. In other words, the reactive functional group introduced into the cellulose-based compound is different from the reactive functional group introduced into the polyvinyl acetal-based compound. Note that while the functional group introduced into the cellulose-based compound and the functional group introduced into the polyvinyl acetal-based compound react, the same functional groups do not react easily. Here, the reason why the same functional groups do not react easily is to prevent bonding between cellulose-based compounds and between polyvinyl acetal-based compounds.

[0056] Then, by bonding the functional group introduced into the cellulose-based compound with the functional group introduced into the polyvinyl acetal-based compound, a polymer compound in which the cellulose-based compound and the polyvinyl acetal-based compound are bonded can be obtained. Specifically, by introducing a thiol group into cellulose to form a cellulose-based compound and a vinyl group into a polyvinyl acetal resin to form a polyvinyl acetal-based compound, the thiol group and the vinyl group bond via 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-based compound and the polyvinyl acetal-based compound are bonded can be obtained by utilizing the bonding reaction between the thiol group and the vinyl group. Of course, it is also possible to introduce a vinyl group into the hydroxyl group of cellulose to form a cellulose-based compound, and then introduce a thiol group into the hydroxyl group of the polyvinyl acetal resin to form a polyvinyl acetal-based compound.

[0057] 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 thiol group that reacts with the vinyl group.

[0058] 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 a hydroxyl group possessed by cellulose, a natural polymer. Note that this chemical modification is different from the chemical modification that introduces the reactive functional group described above, and is a chemical modification for the following alkyl etherification, esterification, etc.

[0059] Examples of bonding of a compound with the hydroxyl group of cellulose include alkyl etherification and esterification. Examples of celluloses having 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 may be used, or two or more types may be used in combination.

[0060] 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 viewpoints of solubility in the organic solvent and smoothness of the dried film of the conductive paste, it is more preferable to use ethyl cellulose as the cellulose.

[0061] 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, as calculated using standard polystyrene standards by GPC, is preferably 10,000 to 100,000, and more preferably 10,000 to 80,000.

[0062] If the number average molecular weight of the cellulose is less than 10,000, the viscosity of the conductive paste may be low, whereas if the number average molecular weight of the cellulose is more than 100,000, the viscosity of the conductive paste may be too high.

[0063] Not all of the hydroxyl groups in cellulose are chemically modified. The glucose rings that make up cellulose have three hydroxyl groups per ring structure, but in the case of chemically modified cellulose, on average, 0.1 to 1 hydroxyl group per ring structure of the glucose rings that make up cellulose remains as hydroxyl groups and is not chemically modified. In this way, reactive functional groups are introduced into the unmodified hydroxyl groups.

[0064] 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 the polyvinyl alcohol.Specific examples include butyralized polyvinyl alcohol (polyvinyl butyral) and formalized polyvinyl alcohol (polyvinyl formal).

[0065] The polyvinyl acetal may be a commercially available product, and various polyvinyl acetals differing in the degree of butyralization, degree of formalization, amount of acetyl groups, amount of hydroxyl groups, molecular weight, 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.

[0066] The polyvinyl acetal is preferably one that is soluble in an organic solvent, and more preferably polyvinyl butyral because of its high solubility in an organic solvent.

[0067] The molecular weight of polyvinyl acetal affects the film strength and the viscosity of the solution, and therefore the number average molecular weight of polyvinyl acetal, as calculated using standard polystyrene standards 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.

[0068] If the number-average molecular weight of the polyvinyl acetal is less than 5,000, the solution viscosity will be extremely low, making it difficult to adjust the viscosity of the inorganic particle-containing composition (paste or slurry). In addition, the strength and adhesion of the film formed by applying and drying the inorganic particle-containing composition may be reduced.

[0069] Polyvinyl acetal has at least one hydroxyl group per molecule. Generally, polyvinyl acetal has 20 to 40 mol % of hydroxyl groups as vinyl alcohol units constituting the polymer. These hydroxyl groups are chemically modified by introducing reactive functional groups.

[0070] The compound that reacts with the hydroxyl groups of cellulose or polyvinyl acetal to chemically modify it can be a compound that has a thiol or vinyl group at one end and a carboxyl group at the other end, and 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.

[0071] An example of a method for synthesizing the polymer compound used in this embodiment will be described below. Cellulose-based compounds and polyvinyl acetal-based compounds can be obtained by esterifying or etherifying the hydroxyl groups of cellulose or polyvinyl acetal with a compound having a functional group reactive with a hydroxyl group and a functional group reactive with other compounds. Examples of functional groups reactive with hydroxyl groups include carboxyl groups and hydroxyl groups.

[0072] The esterification reaction can be carried out using, for example, a condensing agent. Examples of the condensing agent include carbodiimide, diphenylphosphoric acid azide, and 1-hydroxybenzotriazole. One type of condensing agent may be used alone, or two or more types may be used in combination. Among these, carbodiimide is preferred 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.

[0073] Examples of carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide, and N-[3-(dimethylamino)propyl]-N'-ethylcarbodiimide methiodide. Among these, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferred from the viewpoint of availability. When using a carbodiimide, it is also preferred 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.

[0074] On the other hand, the etherification reaction can be carried out efficiently 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.

[0075] To obtain a cellulose-based compound, it is also preferable to dissolve cellulose in an aprotic solvent such as ethyl acetate, mix with a compound having a carboxyl group that forms an ester bond with a hydroxyl group and a vinyl group or a 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 %.

[0076] 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, it is necessary to add 0.3 to 1.7 mol of a compound having a functional group that reacts with other compounds per 1 mol of cellulose.

[0077] The reaction temperature for synthesizing a cellulose-based compound is preferably in the range of room temperature to 50°C. In a system where the synthesis reaction of a cellulose-based compound is completed, a mixture of unreacted cellulose, in which no functional group reactive with other compounds has been introduced to the hydroxyl group, a cellulose-based compound in which one reactive functional group has been introduced, and a cellulose-based compound in which multiple reactive functional groups have been introduced, is present. Chemical modification is a matter of probability, but the majority of cellulose-based compounds have one hydroxyl group of cellulose chemically modified. In the present invention, the mixture of unreacted cellulose, cellulose in which multiple functional groups have been introduced, and cellulose in which one reactive functional group has been introduced is referred to as the cellulose-based compound. Then, once the synthesis of the cellulose-based compound is completed, the solvent can be removed by distillation.

[0078] To synthesize a polyvinyl acetal compound, it is also preferable to dissolve polyvinyl acetal in an aprotic solvent such as ethyl acetate, mix it with a compound having a carboxy group that forms an ester bond with a hydroxyl group and a vinyl group or a 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 %.

[0079] 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 necessarily introduced into all of the polyvinyl acetal, and unreacted polyvinyl acetal is present. In the present invention, a mixture of the unreacted polyvinyl acetal and the polyvinyl acetal into which the functional group has been introduced is used as the polyvinyl acetal compound. After the synthesis of the polyvinyl acetal compound is completed, the solvent can be removed by distillation.

[0080] The polymer compound used in this embodiment can be 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 vinyl group in either the cellulose-based compound or the polyvinyl acetal-based compound to react with a thiol group in the other, resulting in bonding of the cellulose-based compound and the polyvinyl acetal-based compound.

[0081] Alternatively, the polymer compound may be synthesized by dissolving a cellulose compound and a polyvinyl acetal compound in a solvent, adding a nucleophilic agent such as a base such as an amine, and heating the solution.

[0082] The temperature for the reaction to bond the cellulose compound and the polyvinyl acetal compound can be selected appropriately, but is preferably 60° C. or higher, for example.

[0083] Examples of the solvent that can be used include acetate-based solvents such as isobornyl acetate, isobornyl propionate, isobornyl butyrate, and isobornyl isobutyrate, which are solvents that can be used in conductive pastes, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate, and terpene-based solvents such as terpineol, dihydroterpineol, dihydroterpinyl acetate, and terpinyl acetate. If a solvent used in conductive pastes is used as the solvent, the resulting polymer compound can be dissolved in the solvent to form a vehicle.

[0084] 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.

[0085] Specifically, the cellulose-based compound may be 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 with a hydroxyl group of cellulose, and the polyvinyl acetal-based compound may be 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 with a hydroxyl group of polyvinyl acetal. Furthermore, when the first esterification reaction product has a thiol group, the second esterification reaction product may have a vinyl group; when the first esterification reaction product has a vinyl group, the second esterification reaction product may have 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.

[0086] More specifically, the first esterification reaction product may be an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-allyloxypropionic acid and a hydroxy group of ethyl cellulose, and the second esterification reaction product may be an esterification reaction product obtained by dehydration condensation of a carboxy group of 3-mercaptopropionic acid and a hydroxy group of polyvinyl butyral.

[0087] (Cellulose resin, polyvinyl acetal resin) Ideally, the entire binder resin of the conductive paste would be composed of the above-mentioned polymer compound. However, as described above, the synthesis of the polymer compound involves multiple chemical reactions, making it a more expensive compound than general cellulose resin or polyvinyl acetal resin. Therefore, the inventors investigated the use of the above-mentioned polymer compound in combination with a cellulose resin or polyvinyl acetal resin, within the scope that does not impair the contributing function that the polymer compound imparts to the conductive paste.

[0088] In the conductive paste of the present embodiment, the proportion of the polymer compound relative to the total mass of the cellulose resin among the binder resins, one or more resins selected from polyvinyl acetal resins, and the polymer compound is 20 mass% or more, and preferably 30 mass% or more.

[0089] Furthermore, by using a binder resin composed of a cellulose resin, a polyvinyl acetal resin, and the polymer compound, it becomes possible to more freely adjust the viscosity of the conductive paste, which is not possible with the polymer compound alone. In other words, by using the binder resin composition of this embodiment, it is possible to increase the viscosity of the conductive paste compared to when only the polymer compound is used as the binder resin.

[0090] Generally, cellulose resin and polyvinyl acetal resin are not compatible with each other, as described above. However, the polymer compound helps to make the cellulose resin and polyvinyl acetal resin compatible and suppresses phase separation between the cellulose resin and polyvinyl acetal resin. This effect is due to the polymer compound having a cellulose-based compound skeleton and a polyacetal compound skeleton in its molecules. 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 may be limited to a portion of the conductive paste, resulting in unsatisfactory results. 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 may be 99% by mass or less, or 95% by mass or less.

[0091] That is, the content of the polymer compound in the binder resin is 20% by mass or more, more preferably 30% by mass or more, and can be 99% by mass or less, or 95% by mass or less. In other words, the mass ratio of the total of the cellulose resin and the polyvinyl acetal resin to the polymer compound can be set to 1 to 80:20 to 99, more preferably 5 to 70:30 to 95.

[0092] When such phase separation occurs, the binder resin, conductive powder, and ceramic powder are unevenly distributed in the dried film obtained by printing (applying) and drying the conductive paste, and voids where no conductive material is present may occur in the internal electrode obtained by firing the dried film due to the uneven distribution of the binder resin and ceramic powder. The formation of such voids in the internal electrode reduces the area of ​​the internal electrode, which may lead to a decrease in the capacity of the MLCC. The effect of the polymer compound in suppressing phase separation of the cellulose resin and polyvinyl acetal resin contributes to the uniform distribution of conductive powder and ceramic powder particles in the dried film. As a result, the film breakage phenomenon in the internal electrode layer obtained by firing the dried film is resolved, resulting in an increase in the electrostatic capacitance of the MLCC.

[0093] The conductive paste of this embodiment can contain one or more resins selected from cellulose resin and polyacetal resin, which improves the flexibility in adjusting the viscosity of the conductive paste. That is, since the cellulose resin and polyacetal resin can be added appropriately within the range of this embodiment, the viscosity of the conductive paste can be easily adjusted.

[0094] The cellulose resin may be selected from methyl cellulose resin, ethyl cellulose resin, ethyl hydroxyethyl cellulose resin, nitrocellulose resin, etc., and among these resins, ethyl cellulose resin is preferred. Two or more of these resins may be used in combination. Polyvinyl butyral may be selected as the polyvinyl acetal resin. Either the cellulose resin or the polyvinyl acetal resin may be used alone, or both may be used. The blending ratio of the cellulose resin, the polyvinyl acetal resin, and the polymer compound may be appropriately selected as long as it does not deviate from the scope of this embodiment. By selecting these resins and their blending ratios, the viscosity of the conductive paste and the adhesion of the resulting dried film to the green sheet can be appropriately adjusted.

[0095] In this embodiment, in addition to the cellulose resin and polyvinyl acetal resin, it is also possible to add known binder resins such as acrylic resins and maleic acid ester resins. The number average molecular weight of the resins that can be added in this way, in addition to the cellulose resin and polyvinyl acetal resin, is about 20,000 to 300,000 as determined by GCP (gel permeation chromatography) analysis.

[0096] (Organic Solvent) The organic solvent is not particularly limited, and any known organic solvent capable of dissolving the binder resin can be used. Examples of organic solvents include acetate-based solvents such as isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate; terpene-based solvents such as terpineol, dihydroterpineol, dihydroterpinyl acetate, and terpinyl acetate; hydrocarbon-based solvents such as tridecane, nonane, and cyclohexane; and petroleum-based hydrocarbon solvents such as mineral spirits. One or more organic solvents may be used. The solvent selection also takes into consideration compatibility with the ceramic green sheet.

[0097] 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, 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, relative to 100 parts by mass of the conductive powder, the conductivity and dispersibility are excellent.

[0098] The content of the organic solvent 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 content of the organic solvent is 20% by mass or more and 60% by mass or less, based on the total amount of the conductive paste, the conductive paste has excellent conductivity and dispersibility.

[0099] (Dispersant) The conductive paste of this 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 of the inorganic powders and to improve wettability with the organic vehicle, thereby dispersing the inorganic powders in the conductive paste. The dispersant (surfactant) may include an acid-based dispersant including a higher fatty acid, a polymer surfactant, etc., a cationic dispersant other than an acid-based dispersant, a nonionic dispersant, an amphoteric surfactant, a polymer dispersant, etc.

[0100] Furthermore, one or more dispersants may be selected, and the content of the conductive paste may be selected appropriately taking into consideration the viscosity, stickiness, long-term storage stability, etc. of the conductive paste, and may be contained within a range that does not impair the effects of the present invention.

[0101] The mass-average molecular weight of the dispersant is preferably 200 to 100,000. It is more preferably 300 to 30,000. If the mass-average molecular weight is less than 200, the particles may not exhibit sufficient electrostatic repulsion, resulting in reduced particle dispersibility and storage stability. Typically, the dispersant adsorbs to the particle surface to form an adsorption layer, imparting electrostatic and steric repulsion to the particles, resulting in a paste with excellent dispersibility. However, it is believed that over time, collisions between particles overcome the repulsive force of the adsorption layer, causing the particles to aggregate. Therefore, a mass-average molecular weight of 200 or more is preferable. Furthermore, if the mass-average molecular weight is greater than 100,000, compatibility with organic vehicles and organic solvents may decrease, particles may aggregate, and dispersibility and storage stability may decrease. Furthermore, the conductive paste may have an increased viscosity.

[0102] The amount of dispersant added is preferably 0.01 to 5.00 parts by mass, more preferably 0.20 to 2.00 parts by mass, per 100 parts by mass of the conductive metal powder. If the amount of dispersant is less than 0.01 part by mass, it tends to be difficult to obtain sufficient dispersibility. On the other hand, if the amount of dispersant exceeds 5.00 parts by mass, the drying property may be poor and problems such as a decrease in the dry film density may occur.

[0103] The polymer dispersant is preferably anionic and 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, a carboxylic anhydride group is a group formed by the bonding of two carboxyl groups to H. ２ This refers to the anhydride state where O is dehydrated. Examples include acid anhydrides such as phthalic anhydride and maleic anhydride, which are molecular units composed of two dehydrated carboxyl groups.

[0104] Anionic polymer dispersants preferably have graft chains, which are expected to improve solubility in various organic solvents.

[0105] 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, and the dispersibility and storage stability may decrease.

[0106] Such polymer dispersants have carboxyl groups or carboxylic anhydride groups as functional groups on the main chain, and anionic polymer dispersants preferably further have oxyethylene groups on the graft chains in order to adsorb inorganic powders.

[0107] The anionic polymer dispersant may contain one or more types. That is, multiple types of polymer dispersants may be contained 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 taking into consideration the viscosity, stickiness, long-term storage stability, etc. of the conductive paste, and may be contained within a range that does not impair the effects of the present invention.

[0108] Furthermore, the conductive paste of this embodiment may contain a dispersant other than the anionic polymer dispersant. For example, the dispersant (surfactant) may include an acid dispersant including a higher fatty acid, phosphoric acid, a polymer surfactant, etc., a cationic dispersant other than the acid dispersant, a nonionic dispersant, an amphoteric surfactant, a polymer dispersant, etc.

[0109] The content of the dispersant in the conductive paste can be appropriately selected taking into consideration the viscosity, stickiness, long-term storage stability, etc. of the conductive paste, and may be contained within a range that does not impair the effects of the present invention.

[0110] Furthermore, for both anionic polymer dispersants and other dispersants, the mass-average molecular weight of the dispersant is preferably 200 to 100,000. It is more preferably 300 to 30,000. A mass-average molecular weight less than 200 may result in reduced particle dispersibility and storage stability. Typically, a paste with excellent dispersibility is obtained by adsorbing the dispersant to the particle surface to form a dispersant adsorption layer, imparting electrostatic and steric repulsion to the particles. However, it is believed that over time, collisions between particles cause the cohesive forces of the particles to outweigh the repulsive forces of the adsorption layer, resulting in aggregation of the particles. Therefore, a mass-average molecular weight of 200 or greater is preferable. Furthermore, a mass-average molecular weight greater than 100,000 may result in reduced compatibility with organic vehicles and organic solvents, particle aggregation, and reduced dispersibility and storage stability. Furthermore, the paste may also have a high viscosity.

[0111] The total amount of the anionic polymer dispersant and other dispersants 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 the conductive metal powder. If the amount of dispersant is less than 0.01 part 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 property may be poor and problems such as a decrease in the dry film density may occur.

[0112] (Other Additives) Furthermore, additives such as known plasticizers can be added to the conductive paste in order to impart flexibility to the dried film obtained from the conductive paste.

[0113] (Method for Producing Conductive Paste) The method for producing 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 triple-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, allowing the dispersant to be distributed evenly across the surface, making it easier to obtain a uniform conductive paste. Alternatively, the binder resin may be dissolved in an organic solvent for the 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, followed by stirring and kneading using a mixer to produce the conductive paste.

[0114] In addition, the organic solvent for the vehicle is preferably the same as the organic solvent for the paste that adjusts the viscosity of the conductive paste, in order to improve the compatibility of the organic vehicle. 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 relative to 100 parts by mass of the conductive powder. The content of the organic solvent for the vehicle is preferably 10% by mass or more and 40% by mass or less relative to the total amount of the conductive paste.

[0115] The surface smoothness of a dry film formed by printing a conductive paste can be evaluated by its surface roughness. The surface roughness of the conductive paste can be measured, for example, by the method described in the Examples (a method of measuring the arithmetic mean height Sa according to ISO 25178 using a VK-X120 manufactured by Keyence Corporation). When the surface smoothness of the dry film is evaluated by the arithmetic mean height Sa, the value is preferably 0.10 μm or less.

[0116] If the surface roughness is 0.10 μm or less using 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 conductive paste film is low, the dried conductive paste film will adhere to the green sheet as a surface, resulting in excellent adhesion between the dried conductive paste film and the green sheet. Therefore, it is desirable for the surface roughness of the dried conductive paste film to be as low as possible.

[0117] [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.

[0118] In the 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, and for example, barium titanate can be used. In the 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.

[0119] Hereinafter, embodiments of electronic components and the like of the present invention will be described with reference to the drawings. The drawings may be represented schematically or at a different scale as appropriate. Furthermore, 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, and the Z direction is vertical (up and down).

[0120] 1A and 1B are a perspective view and a side cross-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 external electrodes 20.

[0121] A method for manufacturing a multilayer ceramic capacitor 1 using the above-described conductive paste will now be 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, each having this dry film on its upper surface, are stacked and pressure-bonded 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 is then formed on both ends of the ceramic laminate 10 to manufacture the multilayer ceramic capacitor 1. This method will now be described in more detail.

[0122] First, a green sheet is prepared, which is an unfired ceramic sheet made of a dielectric material. Examples of such green sheets include 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, and then coating the paste on a support film such as a PET film in a sheet form and drying it 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.

[0123] Next, the 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 a plurality of sheets. Note that, from the viewpoint of the requirement for thinning of the internal electrode layer 11, the thickness of the conductive paste (dry film) after printing is preferably set to a thickness such that the thickness of the dry film after drying is 1 μm or less.

[0124] Next, 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 thereof are stacked alternately, and then a laminate is obtained by heat and pressure treatment. Note that a configuration in which protective green sheets not coated with conductive paste are further placed on both sides of the laminate may be adopted.

[0125] Next, the laminate is cut to a predetermined size to form green chips, and the green chips are subjected to a binder removal treatment and fired in a reducing atmosphere to produce the ceramic laminate 10. The binder removal treatment is performed in an atmosphere of air or N ２ It is preferable to carry out the debinding treatment in a gas atmosphere. The temperature during the debinding treatment is, for example, 200°C or higher and 400°C or lower. Furthermore, it is preferable to hold the above temperature for 0.5 hours or higher and 24 hours or lower during the debinding treatment. Furthermore, the firing is carried out in a reducing atmosphere to suppress oxidation of the metal used in the internal electrode layers, and the temperature during firing of the laminate is, for example, 1000°C or higher and 1350°C or lower, and the temperature holding time during firing is, for example, 0.5 hours or higher and 8 hours or lower.

[0126] 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. Also, 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 a fired multilayer ceramic body in which a plurality of dielectric layers 12 and internal electrode layers 11 are alternately stacked. Note that, from the viewpoint of taking oxygen into the dielectric layer to increase reliability and suppressing reoxidation of the internal electrodes, the fired multilayer ceramic body may be subjected to an annealing treatment.

[0127] Then, a pair of external electrodes 20 is provided on the produced fired multilayer ceramic body, thereby producing the multilayer ceramic capacitor 1. For example, the external electrodes 20 include 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 electrodes 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.

[0128] EXAMPLES The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0129] <Synthesis of Polymer Compound> [Materials Used] <Conductive Powder> Ni powder (number average particle size of 0.2 μm as measured by SEM) was used as the conductive powder.

[0130] <Ceramic Powder> Ceramic powders include barium titanate (BaTiO ３ The number average particle size measured by SEM was 0.05 μm.

[0131] <Binder Resin> The binder resin was synthesized as follows.

[0132] (Synthesis of Cellulose-Based Compound (1a) Having a Vinyl Group) Ethyl cellulose (Dow Chemical's "Ethocel STD-100", number average molecular weight Mn (value calculated as standard polystyrene by GPC): 63,420, average number of unetherified hydroxyl groups among the hydroxyl groups in one cyclic structure of glucose ring: 0.48) was prepared and dried. Here, the ethyl cellulose was dried in order to remove moisture adsorbed by the ethyl cellulose. Drying was carried out under reduced pressure at room temperature.

[0133] A solution was obtained by dissolving 100 parts by mass of the dried ethyl cellulose in 900 parts by mass of ethyl acetate. To the obtained solution, 0.17 parts by mass of 3-allyloxypropionic acid (corresponding to an average of one 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, and the mixture was stirred at a temperature of 40°C for 5 hours to carry out the reaction. Thereafter, the ethyl acetate was removed to obtain a cellulose-based compound (1a) in which a vinyl group was introduced into ethyl cellulose as a solid.

[0134] A portion of the obtained solid cellulose compound (1a) was analyzed by FT-IR and H-NMR, confirming the formation of an ester bond and the introduction of vinyl groups into ethyl cellulose in an amount equivalent to the moles of the charged 3-allyloxypropionic acid.

[0135] 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.

[0136] (Synthesis of Polyvinyl Butyral Compound (1b) Having Thiol Groups) Polyvinyl butyral ("BM-SZ" manufactured by Sekisui Chemical Co., Ltd., number average molecular weight Mn (measured by GPC in terms of standard polystyrene): 55,000, hydroxyl group content: approximately 22 mol%) was prepared and dried. The polyvinyl butyral was dried in order to remove moisture adsorbed by the polyvinyl butyral. Drying was carried out 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. To the resulting solution, 0.20 parts by mass of 3-mercaptopropionic acid (corresponding to an average of one molecule introduced per polyvinyl butyral molecule), 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, and the mixture was reacted at 40°C for 5 hours with stirring. Thereafter, the ethyl acetate was removed to obtain a polyvinyl butyral compound (1b) in which a thiol group was introduced into polyvinyl butyral as a solid.

[0137] A portion of the obtained solid polyvinyl butyral compound (1b) was analyzed by FT-IR and H-NMR, confirming the formation of an ester bond and the introduction of thiol groups into the polyvinyl butyral in an amount equivalent to the molar amount of the charged 3-mercaptopropionic acid.

[0138] In addition to the compound in which a thiol group is introduced into polyvinyl butyral, the polyvinyl butyral-based compound (1b) also contains unreacted 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.

[0139] (Synthesis of Cellulose-Based Compound (2a) Having a Vinyl Group) Cellulose-based compound (2a) was synthesized in the same manner as for cellulose-based compound (1a), except that 3-allyloxypropionic acid was added in an amount equivalent to an average of two units per molecule of ethyl cellulose.

[0140] (Synthesis of polyvinyl butyral-based compound (2b) having a thiol group) A polyvinyl butyral-based compound (2b) was synthesized in the same manner as for polyvinyl butyral-based compound (1b), except that 3-mercaptopropionic acid was added in an amount corresponding to an average of two thiol groups per one molecule of polyvinyl butyral.

[0141] (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 solvent, and the solution was transferred to a glass flask reaction vessel. After nitrogen substitution, 0.1 parts by mass of azobisisobutyronitrile as a radical generator was added to the solution, and the reaction was carried out at 80°C for 3 hours with stirring to obtain an organic vehicle 1 containing polymer compound 1. Here, the cellulose compound (1a) and polyvinyl butyral compound (1b) had the same molar number. The organic vehicle 1 contained 13.5% by mass of polymer compound 1.

[0142] Here, polymer compound 1 is a mixture of a polymer compound in which a cellulose compound (1a) and a polyvinyl butyral compound (1b) are bonded together, unreacted ethyl cellulose, and unreacted polyvinyl butyral, and in the examples, this mixture is referred to as polymer compound 1. The same applies to polymer compound 2 described below.

[0143] Furthermore, when the produced polymer compound 1 was analyzed by FT-IR and 1H-NMR, the presence of an -S- bond was confirmed, and it was confirmed that the target structure had been obtained. Furthermore, the mass average molecular weight (Mw: standard polystyrene equivalent value measured by GPC) of polymer compound 1 was measured.

[0144] (Synthesis of Polymer Compound 2) Polymer compound 2 synthesized from a cellulose-based compound (2a) and a polyvinyl butyral-based compound (2b) was also synthesized in the same manner as polymer compound 1 to obtain an organic vehicle 2. The content of polymer compound 2 in organic vehicle 2 was 13.5% by mass.

[0145] Furthermore, when the produced polymer compound 2 was analyzed by FT-IR and 1H-NMR, the presence of an -S- bond was confirmed, and it was confirmed that the target structure had been obtained. Furthermore, the mass average molecular weight (Mn: standard polystyrene equivalent value measured by GPC) of polymer compound 2 was measured.

[0146] Table 1 shows the characteristics of the cellulose compounds (1a) and (2a) and the polyvinyl acetal compounds (1b) and (2b) used in polymer compounds 1 and 2, and the mass average molecular weights of the polymer compounds.

[0147]

[0148] Reference Example 1 is an example in which ethyl cellulose and polyvinyl butyral resin are not used as the binder resin, but only polymer compound 1 is used. A conductive paste was prepared as follows, and the physical properties of a dried film obtained using the conductive paste were evaluated.

[0149] <Preparation of Conductive Paste> <Preparation of Conductive Paste 1a> 47 mass% Ni powder, 4.7 mass% ceramic (BT) powder, 26.67 mass% organic vehicle 1, 0.4 mass% anionic polymer dispersant of polymeric polycarboxylic acid (mass average molecular weight 40,000), and the remaining 21.23 mass% organic solvent (dihydroterpineol) were blended to a total of 100 mass%, and these materials were mixed to prepare conductive paste 1a according to Reference Example 1. The prepared conductive paste 1a was printed and dried as follows, and the surface roughness and dry film density of the dried film were evaluated, and the surface of the dried film was observed.

[0150] <Preparation of Conductive Paste 1b> For the conductive paste for cross-sectional observation of the dried film, 25.5 mass% of conductive paste 1a, 46.5 mass% of organic vehicle 1, and 28 mass% of dihydroterpineol were blended to obtain 12 mass% Ni powder, and these materials were mixed to prepare conductive paste 1b according to Reference Example 1. Conductive paste 1b was printed and dried as follows, and the resulting dried film was cut to obtain a sample for cross-sectional observation of the dried film according to Reference Example 1. Conductive paste 1b contained 12 mass% Ni powder and 53.34 mass% of organic vehicle (twice the amount of conductive paste 1a).

[0151] For cross-sectional observation of the dried film, conductive paste 1b was prepared by adding organic vehicle 1 and dihydroterpineol to conductive paste 1a to reduce the Ni powder content in the paste. This is because, even when observing a dried film formed using conductive paste 1a with a Ni powder content of 47% by mass, the Ni powder content is too high, making it difficult to observe the uneven distribution of the binder resin. The same applies to Example 1 and Comparative Examples 1 and 2. When the Ni powder content is 12% by mass, as in conductive paste 1b, it is easy to observe the uneven distribution and phase separation of the binder resin in the cross-section of the dried film. However, for binder resins prone to uneven distribution and phase separation, the tendency to cause problems such as uneven distribution remains unchanged even when the Ni powder content is increased.

[0152] [Evaluation Method] (Dispersibility: Surface Roughness of Dried Film and SEM Observation of Dried Film) <Surface Roughness, SEM Observation of Dried Film Surface> The prepared conductive paste 1a was screen-printed on a 2.54 cm (1 inch) square heat-resistant tempered glass sheet and dried at 120°C in air for 1 hour to prepare a 20 mm square dried film with a film thickness of 1 to 3 μm. When the dispersibility of the conductive paste is good, the surface of the dried film is smooth. When the dispersibility is poor, aggregation 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 prepared dried film was measured using a laser microscope (Keyence VK-X120) in accordance with the ISO 25178 standard. The smaller the surface roughness Sa (arithmetic mean height), the smoother the surface of the dried film. The surface of the obtained dried film was also observed with a SEM (scanning electron microscope).

[0153] <SEM Observation of the Cross Section of the Dry Film> A dry film was prepared using the conductive paste 1b in the same manner as the conductive paste 1a, and the dry film was split to form a cross section, which was then observed by SEM. This observation confirmed the effect of phase separation due to the poor compatibility of ethyl cellulose and polyvinyl butyral resin on the distribution (dispersion) of inorganic particles (Ni particles, BT particles) in the dry film. Note that in Reference Example 1, ethyl cellulose and polyvinyl butyral resin were not used as binders, and only polymer compound 1 was used, so the cross section of the dry film was in the best condition, and was the subject of comparison with the cross sections of the dry films in other examples.

[0154] <Dry Film Density> The prepared conductive paste 1a was placed on a PET film and spread to a length of approximately 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. The PET film was peeled off, and the thickness and weight of each of the four dried films were measured to calculate the dry film density (average value).

[0155] The evaluation results are shown in Tables 2 and 3. Table 2 shows information about the binder resin, the surface roughness of the dried film, and the density of the dried film, while Table 3 shows the type of polymer compound used, the proportion of the polymer compound in the binder resin, the total proportion of ethyl cellulose and polyvinyl butyral resin in the binder resin, an SEM image of the surface of the dried film, and an SEM image of the cross section of the dried film. The binder resin contained in the conductive paste 1a according to Reference Example 1 was 3.6% by mass.

[0156] Comparative Example 1 Comparative Example 1 is an example in which ethyl cellulose and polyvinyl butyral resin were used as binder resins, and neither polymer compound 1 nor polymer compound 2 was used. A conductive paste was prepared as follows, and the physical properties of a dried film obtained using the conductive paste were evaluated.

[0157] <Preparation of Conductive Paste> <Preparation of Conductive Paste 2a> 5 parts by mass of ethyl cellulose (EC "Ethocel STD-100" manufactured by Dow Chemical, number average molecular weight Mn (value calculated by GPC in terms of standard polystyrene): 63,420, average number of unetherified hydroxyl groups among the hydroxyl groups per molecule of the cyclic structure of glucose ring: 0.48) was dissolved in 30 parts by mass of terpineol to prepare organic vehicle 3a. 4.35 parts by mass of polyvinyl butyral resin (PVB "BM-SZ" manufactured by Sekisui Chemical Co., Ltd., number average molecular weight Mn (value calculated by GPC in terms of standard polystyrene): 55,000, amount of hydroxyl groups: approximately 22 mol%) was dissolved in 30 parts by mass of terpineol to prepare organic vehicle 3b. Then, organic vehicle 3a and organic vehicle 3b were mixed in equal amounts to prepare organic vehicle 3.

[0158] 47% by mass of Ni powder, 4.7% by mass of ceramic (BT) powder, 26.67% by mass of organic vehicle 3, 0.4% by mass of an anionic polymer dispersant of molecular polycarboxylic acid (mass average molecular weight 40,000), and the remaining 21.23% by mass of organic solvent (dihydroterpineol) were blended together to make a total of 100% by mass, and these materials were mixed to prepare conductive paste 2a.

[0159] <Preparation of Conductive Paste 2b> As a conductive paste for cross-sectional observation of a dried film, 25.5% by mass of conductive paste 2a, 46.5% by mass of organic vehicle 3, and 28% by mass of dihydroterpineol were blended so that the Ni powder was 12% by mass, and these materials were mixed to prepare conductive paste 2b according to Comparative Example 1.

[0160] Using the obtained conductive pastes 2a and 2b, the surface roughness of the dried film of Comparative Example 1 was measured, the surface and cross section of the dried film were observed with an SEM, and the density of the dried film was measured in the same manner as in Reference Example 1.

[0161] Example 1 is an example in which ethyl cellulose, polyvinyl butyral resin, and polymer compound 1 are used as binder resins. A conductive paste was prepared as follows, and the physical properties of a dried film obtained using the conductive paste were evaluated.

[0162] <Preparation of Conductive Paste> <Preparation of Conductive Paste 3a> 47 mass% of Ni powder, 4.7 mass% of ceramic (BT) powder, 8 mass% of organic vehicle 1, 18.67 mass% of organic vehicle 3, 0.4 mass% of an anionic polymer dispersant of high molecular weight polycarboxylic acid (mass average molecular weight 40,000), and the remaining 21.23 mass% of organic solvent (dihydroterpineol) were blended together to make a total of 100 mass%, and these materials were mixed to prepare conductive paste 3a according to Example 1.

[0163] The total amount of binder resin contained in the conductive paste 3a was 3.6% by mass, with 1.08% by mass of conductive polymer compound 1, 1.35% by mass of ethyl cellulose, and 1.17% by mass of polyvinyl butyral resin. The proportion of polymer compound 1 in the binder resin was 30% by mass, and the combined proportion of ethyl cellulose and polyvinyl butyral resin in the binder resin was 70% by mass. In the polymer compound 1 used in Example 1, the average number of functional groups introduced into the cellulose-based compound and polyvinyl butyral-based compound was 1, i.e., one vinyl group was introduced per molecule of ethyl cellulose, and one thiol group was introduced per molecule of polyvinyl butyral.

[0164] <Preparation of Conductive Paste 3b> As a conductive paste for cross-sectional observation of a dried film, 25.5 mass% of Conductive Paste 3a, 14.0 mass% of Organic Vehicle 1, 32.5 mass% of Organic Vehicle 3, and 28 mass% of dihydroterpineol were blended so that the Ni powder was 12 mass%, and these materials were mixed to prepare Conductive Paste 3b according to Example 1.

[0165] Using the obtained conductive pastes 3a and 3b, the surface roughness of the dried film of Example 1 was measured, the surface and cross section of the dried film were observed with an SEM, and the density of the dried film was measured in the same manner as in Reference Example 1.

[0166] Comparative Example 2 Comparative Example 2 is an example in which ethyl cellulose, polyvinyl butyral resin, and polymer compound 2 are used as binder resins. A conductive paste was prepared as follows, and the physical properties of a dried film obtained using the conductive paste were evaluated.

[0167] <Preparation of Conductive Paste> <Preparation of Conductive Paste 4a> 47 mass% Ni powder, 4.7 mass% ceramic (BT) powder, 8 mass% organic vehicle 2, 18.67 mass% organic vehicle 3, 0.4 mass% anionic polymer dispersant of high molecular weight polycarboxylic acid (mass average molecular weight 40,000), and the remaining 21.23 mass% organic solvent (dihydroterpineol) were blended together to make a total of 100 mass%, and these materials were mixed to prepare conductive paste 4a according to Comparative Example 2.

[0168] The total amount of binder resin contained in the conductive paste 4a was 3.6% by mass, with 1.08% by mass of conductive polymer compound 2, 1.35% by mass of ethyl cellulose, and 1.17% by mass of polyvinyl butyral resin. The proportion of polymer compound 2 in the binder resin was 30% by mass, and the combined proportion of ethyl cellulose and polyvinyl butyral resin in the binder resin was 70% by mass. Note that the polymer compound 2 used in Comparative Example 2 had an average of two functional groups introduced into the cellulose-based compound and polyvinyl butyral-based compound, i.e., two vinyl groups were introduced per molecule of ethyl cellulose, and two thiol groups were introduced per molecule of polyvinyl butyral.

[0169] Using the obtained conductive paste 4a, the surface roughness and density of the dried film of Comparative Example 2 were measured in the same manner as in Reference Example 1.

[0170]

[0171]

[0172] [Evaluation Results] As shown in Table 2, the dried films formed using the conductive pastes of Reference Example 1 and Example 1 had a surface roughness Sa (arithmetic mean height) of 0.1 μm or less, and a dry film density of 5 g / cm compared to Comparative Example 1. ３ The results were high, at or above 100%. Furthermore, Comparative Example 2, in which an average of two functional groups were introduced into the polymer compound, had a high dry film density but poor surface roughness. A higher dry film density is preferable because it reduces shrinkage during firing.

[0173] Table 3 shows images of the surface and cross section of the dried film in Reference Example 1, Example 1, and Comparative Example 1, obtained by SEM observation. Although a polymer compound was used in Comparative Example 2, the surface roughness was inferior to that of Example 1 and Reference Example 1, so SEM observation of the surface and cross section of the dried film was not performed, and the results are not shown in Table 3. As can be seen from the SEM photograph of the cross section shown in Table 3, the dried film in Example 1 has fewer irregularities than the dried film in Comparative Example 1.

[0174] Furthermore, in the cross-sectional SEM photographs in Table 3, it can be seen that both Reference Example 1 and Example 1 have fine voids scattered throughout the dried film, whereas Comparative Example 1 has voids of approximately 20 μm in the thickness direction.

[0175] From the above results, it is considered that voids without conductive material are unlikely to occur in the internal electrode film obtained by firing the dry film of Reference Example 1 and Example 1, but that voids without conductive material are likely to occur in the internal electrode film obtained by firing the dry film of Comparative Example 1, which are caused by voids of about 20 μm in the thickness direction of the dry film. The voids of about 20 μm seen in the cross-sectional SEM photograph of Comparative Example 1 shown in Table 3 are considered to be voids formed due to phase separation caused by poor compatibility between ethyl cellulose and polyvinyl butyral resin, which are binder resins of the conductive paste according to Comparative Example 1.

[0176] As described above, the conductive paste of the present invention can be suitably used as a raw material for internal electrodes of multilayer ceramic capacitors, which are chip components (electronic components) in electronic devices such as mobile phones and digital devices, and is therefore industrially useful.

[0177] 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 Plated layer

Claims

1. A conductive paste comprising a conductive powder, a ceramic powder, a dispersant, a binder resin, and an organic solvent, wherein the binder resin includes one or more resins selected from a cellulose resin and a polyvinyl acetal resin, and a polymer compound in which a cellulose-based compound and a polyvinyl acetal-based compound are bonded by a sulfur atom, and in the polymer compound, a molar ratio of the sulfur atom to the cellulose-based compound is 0.3 to 1.7, and the polymer compound is contained in an amount of 20% by mass or more based on the total mass of the cellulose resin, the polyvinyl acetal resin, and the polymer compound.

2. The cellulose-based compound is a cellulose derivative having a thiol group or a vinyl group, the polyvinyl acetal-based compound is a polyvinyl acetal resin having a thiol group or a vinyl group, and 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 conductive paste according to claim 1.

3. The cellulose derivative is ethyl cellulose having a thiol group or a vinyl group, and the polyvinyl acetal resin is polyvinyl butyral having a thiol group or a vinyl group. The conductive paste according to claim 2.

4. The cellulose-based compound is a first esterification reactant obtained by dehydration condensation of a carboxyl group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of cellulose, the polyvinyl acetal-based compound is a second esterification reactant obtained by dehydration condensation of a carboxyl group of a carboxylic acid having a thiol group or a vinyl group and a hydroxyl group of polyvinyl acetal, and when the first esterification reactant has a thiol group, the second esterification reactant has a vinyl group, and when the first esterification reactant has a vinyl group, the second esterification reactant has a thiol group, and the polymer compound is a thiol-ene reactant of the first esterification reactant and the second esterification reactant. The conductive paste according to claim 1.

5. The first esterification reactant is an esterification reactant formed by the dehydration condensation of the carboxy group of 3-allyloxypropionic acid and the hydroxyl group of ethyl cellulose, and the second esterification reactant is an esterification reactant formed by the dehydration condensation of the carboxy group of 3-mercaptopropionic acid and the hydroxyl group of polyvinyl butyral. The conductive paste according to claim 4.

6. The conductive paste according to claim 1, wherein the cellulose resin is an ethyl cellulose resin and the polyvinyl acetal resin is a polyvinyl butyral resin.

7. The conductive paste according to claim 1, wherein the conductive powder is nickel powder.

8. The conductive paste according to claim 1, wherein the number average particle diameter of the conductive powder is 0.05 μm or more and 1.0 μm or less.

9. The conductive paste according to claim 1, wherein the ceramic powder contains barium titanate.

10. The conductive paste according to claim 1, wherein the number average particle diameter of the ceramic powder is 0.01 μm or more and 0.5 μm or less.

11. 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.

12. The conductive paste according to claim 1, which is for an internal electrode of a multilayer ceramic component.

13. An electronic component formed using the conductive paste according to claim 1.

14. A multilayer ceramic capacitor having at least a laminate in which a dielectric layer and an internal electrode layer are laminated, wherein the internal electrode layer is formed using the conductive paste according to claim 1.

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