JP5139775B2 - Inorganic powder dispersion paste - Google Patents

Description

The present invention is an inorganic powder-dispersed paste that is less prone to problems such as sheet attack and delamination, has excellent surface smoothness after coating and drying, has little residual carbon after firing, and can be degreased at low temperatures About.

Polyvinyl acetal resin is excellent in toughness, film-forming properties, dispersibility of inorganic and organic powders such as pigments, and adhesion to the coated surface. For example, a ceramic green sheet constituting a multilayer ceramic capacitor And conductive paste, ink, paint, baking enamel, wash primer, etc.

In particular, a multilayer ceramic capacitor is generally manufactured through the following steps.
First, a ceramic slurry composition is obtained by adding ceramic raw material powder to binder resin, such as polyvinyl butyral resin, and mixing uniformly. The obtained ceramic slurry composition is coated on the release-treated support surface. This is heated to remove volatile components such as a solvent, and then peeled off from the support to obtain a ceramic green sheet. Next, on the obtained ceramic green sheet, a plurality of sheets of conductive paste containing polyvinyl butyral resin or the like applied as a binder resin are alternately stacked, and heat-pressed to produce a laminate, which is degreased. Then, a multilayer ceramic capacitor is obtained through a step of sintering an external electrode on the end face of the fired ceramic product obtained by firing.

In recent years, there has been a demand for higher capacity of multilayer ceramic capacitors, and further multilayering and thinning have been studied. In such multilayer ceramic capacitors, the ceramic ceramic sheet was formed on the surface. Due to insufficient adhesion between the conductive paste layer and the region where the conductive paste layer is not formed, delamination called delamination may occur.

On the other hand, Patent Document 1 and Patent Document 2 disclose a method for improving adhesion by using a modified polyvinyl acetal resin as a binder resin of a conductive paste. However, the surface of the conductive paste layer obtained after coating and drying has irregularities, so that there are problems that it is inferior in so-called leveling properties, and there is a problem that the residual carbon content after sintering increases.

Further, it has been studied to reduce the residual carbon content after sintering by using an acrylic resin having excellent thermal decomposability as the binder resin. However, the acrylic resin has poor adhesion to the ceramic green sheet, and delamination could not be prevented.

In addition, with the recent thinning of multilayer ceramic capacitors, the so-called sheet attack phenomenon, in which the organic solvent of the conductive paste dissolves the ceramic green sheet, has become a new major issue. When the acetal resin is used alone, the sheet attack resistance is insufficient. Therefore, it is necessary to use an organic solvent for the conductive paste that does not easily generate a sheet attack.

On the other hand, for example, Patent Document 3 discloses a method in which an acrylic resin and a butyral resin are mixed as a binder resin of a conductive paste.
However, in such a method, the compatibility between the acrylic resin and the butyral resin is still low. In addition, when the binder resin described in Patent Document 3 and an organic solvent that does not easily generate a sheet attack are used in combination as a material for a conductive paste, the solubility of the acrylic resin in the organic solvent is reduced. As a result, there has been a problem in that phase separation occurs in the conductive paste or irregularities are formed on the surface of the conductive paste layer obtained after coating and drying.
JP-A-2005-113133 JP 2005-298792 A JP 2006-278162 A

In view of the above situation, the present invention is less likely to cause problems such as sheet attack and delamination, has excellent surface smoothness after coating and drying, has little residual carbon after firing, and can be degreased at low temperatures. It is an object to provide an inorganic powder dispersion paste.

The present invention is an inorganic powder-dispersed paste containing a polyvinyl acetal resin, a (meth) acrylic resin, an organic solvent having a boiling point of 150 ° C. or higher, and an inorganic powder, wherein the polyvinyl acetal resin has a hydroxyl group content of 25 mol%. It is the following polyvinyl acetal resin, and the (meth) acrylic resin has a segment derived from methyl methacrylate, a segment derived from a (meth) acrylic monomer having a hydroxyl group, and a carbon number of 4 to 16, and a hydroxyl group It has a segment derived from a (meth) acrylic monomer not containing 15 to 70% by weight of a segment derived from methyl methacrylate and 30% by weight or less of a segment derived from a (meth) acrylic monomer having a hydroxyl group It is the inorganic powder dispersion paste to contain.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have found that when a polyvinyl acetal resin and a (meth) acrylic resin having a predetermined structure are used as a binder resin, they are not only highly compatible with each other but also are difficult to generate sheet attack. Even when used in combination with a solvent, it can realize excellent solubility, can effectively prevent the occurrence of sheet attack and delamination, and can realize high surface smoothness after coating and drying, and after firing The present inventors have found that the amount of residual carbon is small and can be degreased at a low temperature, thereby completing the present invention.

The inorganic powder paste of the present invention contains a polyvinyl acetal resin and a (meth) acrylic resin as a binder resin.

The polyvinyl acetal resin is a polyvinyl acetal resin having a hydroxyl group content of 25 mol% or less. Such a polyvinyl acetal resin is excellent in compatibility with the (meth) acrylic resin described later, and has high adhesion, so that it is possible to effectively prevent the occurrence of delamination.
When the amount of the hydroxyl group exceeds 25 mol%, compatibility with (meth) acrylic resin, which will be described later, and adhesion are deteriorated. A preferable upper limit is 25 mol%. Moreover, a preferable minimum is 20 mol%.

Among the polyvinyl acetal resins having a hydroxyl group content of 25 mol% or less, examples of commercially available resins include Eslek BL-S and BH-S (both manufactured by Sekisui Chemical Co., Ltd.).

The polyvinyl acetal resin of the present invention is obtained by acetalizing polyvinyl alcohol. A preferable lower limit of the degree of saponification of the polyvinyl alcohol used is 80 mol%. If it is less than 80 mol%, acetalization becomes difficult because the water solubility of polyvinyl alcohol deteriorates, and acetalization itself becomes difficult because the amount of hydroxyl groups decreases. A more preferred lower limit is 85 mol%.

The acetalization method is not particularly limited, and a conventionally known method can be used. For example, an aqueous solution of polyvinyl alcohol, an alcohol solution, a water / alcohol mixed solution, a dimethyl sulfoxide (DMSO) solution in the presence of an acid catalyst. Examples thereof include a method of adding various aldehydes.

In the present invention, the aldehyde used for the acetalization is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal Glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde and the like. Of these, acetaldehyde and butyraldehyde are preferable.

The preferable lower limit of the degree of acetalization of the polyvinyl acetal resin is 65 mol%, and the preferable upper limit is 80 mol%. If it is less than 65 mol%, the resulting polyvinyl acetal resin becomes water-soluble and insoluble in an organic solvent, which may hinder paste preparation. When it exceeds 80 mol%, the residual hydroxyl group is decreased, the toughness of the polyvinyl acetal resin is impaired, and the coating strength at the time of paste printing may be lowered. A more preferred lower limit is 70 mol%, and a more preferred upper limit is 78 mol%.
In the present specification, the degree of acetalization is the ratio of the number of hydroxyl groups acetalized with aldehydes among the number of hydroxyl groups of polyvinyl alcohol, and the calculation method of the degree of acetalization is the acetal of polyvinyl acetal resin. Since the group is formed by acetalization from two hydroxyl groups, a method of counting the two acetalized hydroxyl groups is employed to calculate the mol% of the degree of acetalization.

As the polyvinyl acetal resin having a hydroxyl group content of 25 mol% or less, a modified polyvinyl acetal resin obtained by acetalizing a modified polyvinyl alcohol having an ethylene content of 1 to 20 mol% and a saponification degree of 80 mol% or more is used. preferable. Such a modified polyvinyl acetal resin maintains compatibility with the (meth) acrylic resin described later and has higher adhesion, and therefore can effectively prevent the occurrence of delamination.

The preferable lower limit of the ethylene unit content of the modified polyvinyl alcohol is 1 mol%, and the preferable upper limit is 20 mol%. The modified polyvinyl alcohol contains an ethylene unit, so that the solution viscosity of the modified polyvinyl acetal resin obtained by acetalization increases, so that the coating film when used as a dispersibility of inorganic powder or as a paste for coating. The strength of is improved.

When the ethylene unit content is less than 1 mol%, the dispersibility of the inorganic powder, the printability of the conductive paste, and the strength of the coating film may be lowered. If it exceeds 20 mol%, the water-solubility of the modified polyvinyl alcohol will be reduced, making acetalization difficult, or the solubility of the resulting modified polyvinyl acetal resin in an organic solvent will be reduced, which hinders the preparation of a conductive paste. And viscosity stability over time may be reduced. A more preferred lower limit is 2 mol%, and a more preferred upper limit is 10 mol%.

A preferable lower limit of the saponification degree of the modified polyvinyl alcohol is 80 mol%. If it is less than 80 mol%, the water-solubility of the modified polyvinyl alcohol deteriorates, so that acetalization becomes difficult, and the acetalization itself may be difficult because the amount of hydroxyl groups decreases. A more preferred lower limit is 85 mol%.

The modified polyvinyl alcohol may be used alone or in combination of two or more modified polyvinyl alcohols as long as the ethylene unit content is within the above range and the saponification degree is 80 mol% or more. You may mix and use alcohol, and after adjusting ethylene unit content in the said range, and adjusting to the modification polyvinyl alcohol whose saponification degree is 80 mol% or more, you may use.

The modified polyvinyl alcohol can be obtained by saponifying a copolymer of vinyl ester and ethylene. The vinyl ester is not particularly limited, and examples thereof include vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate. Of these, vinyl acetate is preferable from the economical viewpoint.

The modified polyvinyl alcohol is preferably modified with only ethylene. Modified polyvinyl alcohol modified only with ethylene is excellent in water solubility, and a solution obtained by dissolving the resulting modified polyvinyl acetal resin in an organic solvent is excellent in viscosity stability over time. When the modified polyvinyl alcohol is further modified with a comonomer other than ethylene, the preferable upper limit of the content of the comonomer is 2.0 mol%. When it exceeds 2.0 mol%, water solubility will deteriorate and the viscosity stability with time of the solution which melt | dissolved the modified polyvinyl acetal resin obtained in the organic solvent may be inferior.

The modified polyvinyl alcohol may be one obtained by copolymerizing an ethylenically unsaturated monomer as long as the effects of the present invention are not impaired. The ethylenically unsaturated monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile methacrylonitrile, acrylamide, and methacrylamide. , Trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, fluoride Examples include vinyl, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate, and the like. Also use terminal-modified polyvinyl alcohol obtained by copolymerizing vinyl ester monomer such as vinyl acetate with ethylene in the presence of thiol compounds such as thiol acetic acid and mercaptopropionic acid, and saponifying it. Can do.

When the modified polyvinyl alcohol is used, a modified polyvinyl alcohol having an ethylene content of 1 to 20 mol% and a saponification degree of 80 mol% or more may be used alone, or two or more kinds of modified polyvinyl alcohol may be used. The modified polyvinyl acetal resin finally obtained by mixing or mixing the modified polyvinyl alcohol and unmodified polyvinyl alcohol has an ethylene content of 1 to 20 mol% and a saponification degree of 80 mol% or more. It may be.

The modified polyvinyl acetal resin is obtained by acetalizing the modified polyvinyl alcohol. The acetalization method is not particularly limited, and a conventionally known method can be used. For example, an aqueous solution of polyvinyl alcohol, an alcohol solution, a water / alcohol mixed solution, a dimethyl sulfoxide (DMSO) solution in the presence of an acid catalyst. Examples thereof include a method of adding various aldehydes.

In the present invention, the aldehyde used for the acetalization is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal Glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde and the like. Of these, acetaldehyde and butyraldehyde are preferable.

The preferable lower limit of the degree of acetalization of the modified polyvinyl acetal resin is 65 mol%, and the preferable upper limit is 80 mol%. If it is less than 65 mol%, the resulting modified polyvinyl acetal resin becomes water-soluble and insoluble in an organic solvent, which may hinder paste preparation. When it exceeds 80 mol%, the residual hydroxyl group is decreased, the toughness of the modified polyvinyl acetal resin is impaired, and the coating strength at the time of paste printing may be lowered. A more preferred lower limit is 70 mol%, and a more preferred upper limit is 78 mol%.

The content of the polyvinyl acetal resin in the inorganic powder-dispersed paste of the present invention is not particularly limited because it depends on the type and specific gravity of the inorganic powder to be used, but the preferred lower limit is 1% by weight and the preferred upper limit is 20% by weight. If it is less than 1% by weight, the adhesion may be reduced and delamination may occur, and if it exceeds 20% by weight, the fluidity may be reduced and printing may be affected. However, if the required performance such as adhesion is satisfied, it is more preferable that the solid content is smaller in terms of sinterability.

The (meth) acrylic resin is a segment derived from methyl methacrylate, a segment derived from a (meth) acrylic monomer having a hydroxyl group, and a (meth) acrylic monomer having 4 to 16 carbon atoms and not containing a hydroxyl group. It has a segment derived from.
Since such a (meth) acrylic resin is excellent in thermal decomposability, the inorganic powder-dispersed paste of the present invention has very little residual carbon after firing and can be degreased at a low temperature. Moreover, the low fluidity | liquidity of polyvinyl acetal resin can be improved and printability can be improved.
Furthermore, since the (meth) acrylic resin is also excellent in surface smoothness, the coating obtained after applying the inorganic powder dispersion paste of the present invention has less surface irregularities. In addition, even when an organic solvent that does not easily generate sheet attack is used as the organic solvent, it has high compatibility, and phase separation does not occur during storage.
In the present specification, “degreasing at low temperature” means that the firing temperature at which 99.5% by weight of the initial weight of the inorganic powder-dispersed paste of the present invention has disappeared is low. Specifically, it refers to a case where the firing temperature at which 99.5% by weight of the initial weight of the binder resin composition disappears is 250 to 400 ° C. in a normal air atmosphere in which nitrogen substitution or the like is not performed.
Moreover, in this specification, (meth) acryl means acryl or methacryl.

The (meth) acrylic resin has a segment derived from methyl methacrylate.
Although the above methyl methacrylate is a resin that decomposes at low temperatures, its higher order structure brings about a function of increasing the decomposition temperature. Therefore, the higher order structure of methyl methacrylate is eliminated by copolymerizing with other components described later, and the low temperature Decomposition characteristics can be sufficiently exhibited, and degreasing at a lower temperature can be realized.

The lower limit of the content of segments derived from methyl methacrylate in the (meth) acrylic resin is 15% by weight, and the upper limit is 70% by weight. If it is less than 15% by weight, the residual carbon after sintering increases, and if it exceeds 70% by weight, the thermal decomposition temperature becomes high.

The (meth) acrylic monomer having a hydroxyl group is not particularly limited. For example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 2, 3-dihydroxypropyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, polyethylene glycol-polypropylene glycol monoacrylate, polyethylene glycol-polytetramethylene glycol monoacrylate, polypropylene glycol-polytetramethylene glycol monoacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxy Propyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, 2,3-dihydroxypropyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, polyethylene glycol-polypropylene glycol monomethacrylate, polyethylene glycol-polytetramethylene glycol monomethacrylate And polypropylene glycol-polytetramethylene glycol monomethacrylate. Among these, methacrylate is preferable from the viewpoint of sinterability, and specifically, for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, and polypropylene glycol monomethacrylate are preferable.

The upper limit of the content of the segment derived from the (meth) acrylic monomer having a hydroxyl group in the (meth) acrylic resin is 30% by weight. If it exceeds 30% by weight, the residual carbon after sintering increases. A preferred lower limit is 1% by weight and a preferred upper limit is 20% by weight. If it is less than 1% by weight, the compatibility with the polyvinyl acetal resin may deteriorate.

The (meth) acrylic monomer having 4 to 16 carbon atoms and not containing a hydroxyl group is not particularly limited as long as it is other than the above methyl methacrylate. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate , Isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, isodecyl acrylate, isobornyl acrylate, tetrahydrofuryl acrylate , Ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate Isobutyl methacrylate, t- butyl methacrylate, n- hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, isodecyl methacrylate, isobornyl methacrylate, tetrahydrofuryl methacrylate. Among these, methacrylate is preferable from the viewpoint of sinterability. Specifically, for example, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate are preferred.

The preferable lower limit of the content of the segment derived from the (meth) acrylic monomer having 4 to 16 carbon atoms in the (meth) acrylic resin and not containing a hydroxyl group is preferably 70% by weight. is there. If it is less than 15% by weight, the residual carbon after sintering may increase, and if it exceeds 70% by weight, the thermal decomposition temperature may increase. A more preferred lower limit is 20% by weight, and a more preferred upper limit is 50% by weight.

The polymerization method of the (meth) acrylic resin is not particularly limited, and examples thereof include a method used for polymerization of a normal (meth) acrylate monomer. For example, a free radical polymerization method, a living radical polymerization method, an iniferter polymerization method, Examples thereof include an anionic polymerization method and a living anionic polymerization method.
When a polymerization initiator is used for the polymerization of the (meth) acrylic resin, the polymerization initiator is not particularly limited. The polymerization initiator may be added all at once during the polymerization of the (meth) acrylic resin, or may be added in several divided portions. When the polymerization initiator is added in several portions, the (meth) acrylic resin containing no low molecular weight components such as residual oligomers can be obtained.

Although it does not specifically limit as a number average molecular weight by polystyrene conversion of the said (meth) acrylic resin, A preferable minimum is 5000 and a preferable upper limit is 100,000. If it is less than 5000, sufficient viscosity may not be obtained, and if it exceeds 100,000, the compatibility may deteriorate.
In addition, the number average molecular weight by polystyrene conversion can be obtained by GPC measurement using, for example, a column LF-804 manufactured by SHOKO as a column. The same applies hereinafter.

The content of the (meth) acrylic resin in the inorganic powder-dispersed paste of the present invention is not particularly limited because it depends on the type and specific gravity of the inorganic powder to be used, the amount of the polyvinyl acetal resin to be used together, etc. A preferred upper limit is 20% by weight. If it is less than 1% by weight or more than 20% by weight, it may be difficult to print using the inorganic powder dispersion paste.

Further, the content of the entire binder resin in the inorganic powder-dispersed paste of the present invention is not particularly limited because it is determined by the type and specific gravity of the inorganic powder to be used, but the preferred lower limit is 1% by weight and the preferred upper limit is 40% by weight. . If it is less than 1% by weight, the dispersibility of the inorganic powder may be lowered, and if it exceeds 40% by weight, the performance such as conductivity may be lowered.

The inorganic powder-dispersed paste of the present invention contains an organic solvent having a boiling point of 150 ° C. or higher.
Examples of the organic solvent having a boiling point of 150 ° C. or higher include, for example, menthene, menthane, menthone, myrcene, α-pinene, α-terpinene, γ-terpinene, limonene, perillyl acetate, menthyl acetate, carbyl acetate, and dihydrocarbyl acetate. Peryl alcohol, dihydroterpineol acetate, terpineol acetate, dihydroterpineol, terpinyloxyethanol, dihydroterpinyloxyethanol, terpinyl methyl ether, dihydroterpinyl methyl ether, dihydroterpinyl propionate, iso Bonyl propionate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, novir acetate, octyl acetate, dimethyl octyl Acetate, butyl carbitol acetate, acetoxy-methoxyethoxy-cyclohexanol acetate, dihydrocarbol, 2-ethylhexyl glycol, benzyl glycol, phenylpropylene glycol, methyl decalin, amylbenzene, cumene, cymene, 1,1-diisopropylhexane, citronellol Etc. These may be used alone or in combination of two or more.

Among these, terpenes having no polar substituents such as hydroxyl groups represented by dihydroterpineol acetate, terpineol acetate, terpinyl methyl ether, dihydroterpinyl methyl ether and the like and hydrogenated products thereof are particularly preferable. Dihydroterpineol acetate is preferably used. The dihydroterpineol acetate is excellent in compatibility with the polyvinyl acetal resin and (meth) acrylic resin used in the present invention, but the binder resin used for ceramic green sheets is difficult to dissolve, so dihydroterpineol acetate is used. By doing so, compatibility with the binder resin and sheet attack resistance can both be achieved.

The inorganic powder dispersion paste of the present invention contains an inorganic powder.
The material of the inorganic powder is not particularly limited. For example, gold, silver, copper, nickel, palladium, alumina, silica, zirconia, barium titanate, alumina nitride, silicon nitride, boron nitride; silicate glass, lead glass _{, CaO · Al 2 O 3 ·} SiO 2 type inorganic _{glass, MgO · Al 2 O 3 ·} SiO 2 type inorganic _glass, glass powder (low melting glass), such as _{LiO 2 · Al 2 O 3 ·} SiO 2 type inorganic glass; Various metal blacks such as carbon black, carbon nanotubes, titanium oxide, zirconium oxide, metal complexes, Y ₂ O ₂ S: Eu, (SrCaBaMg) ₅ (PO ₄ ) ₃ Cl: Eu, LaPO ₄ : Ce, Tb, _{Y 2 O 3: Eu, Ca} 10 (PO 4) 6 FCl: Sb, Mn, BaMgAl 10 O 17: Eu, Zn 2 Si _{4: Mn, (Y, Gd} ) BO 3: Eu, CaWO 4, Gd 2 O 2 S: Tb, (Y, Sr) TaO 4: phosphor such as Nb and the like.

The content of the inorganic powder in the inorganic powder-dispersed paste of the present invention is not particularly limited because it is determined by the type and specific gravity of the inorganic powder to be used and the printing process, but the preferred lower limit is 5% by weight and the preferred upper limit is 95%. %. If the content of the inorganic powder is less than 5% by weight, a sufficient viscosity cannot be obtained, and printability is deteriorated, or there are problems such as a large amount of organic components resulting in an increase in residual organic content. There is. If it exceeds 95% by weight, it may be difficult to disperse the inorganic powder.

Moreover, the inorganic powder dispersion paste of the present invention may contain an additive such as a surfactant. The surfactant is not particularly limited, and examples thereof include a cationic surfactant, an anionic surfactant, and a nonionic surfactant.

The viscosity of the inorganic powder-dispersed paste of the present invention is not particularly limited, but the preferred lower limit of the viscosity when measured with a B-type viscometer at 20 ° C. and setting the probe rotation speed to 5 rpm is preferably 0.1 Pa · s. The upper limit is 100 Pa · s. When the viscosity is less than 0.1 Pa · s, it may be difficult for the inorganic powder dispersion paste to maintain a predetermined shape after coating by a die coating method or the like. Printability such as coating may be inferior.

It does not specifically limit as a coating method of the inorganic powder dispersion paste of this invention, For example, screen printing, die coat printing, offset printing, gravure printing, inkjet printing etc. are mentioned.

The method for producing the paste of the present invention is not particularly limited, and a polyvinyl acetal resin, (meth) acrylic resin, dihydroterpineol acetate, inorganic powder, and various additives are conventionally known stirring methods, specifically, for example, 3 Kneading may be performed with a main roll or the like.

According to the present invention, an inorganic powder that is less prone to problems such as sheet attack and delamination, has excellent surface smoothness after coating and drying, has little residual carbon after firing, and can be degreased at low temperatures. A dispersion paste can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
([Synthesis Example 1] Synthesis of polyvinyl acetal resin)
193 g of a modified polyvinyl alcohol resin having a polymerization degree of 1700, an ethylene content of 10 mol% and a saponification degree of 88 mol% was added to 2900 g of pure water, and the mixture was stirred and dissolved at a temperature of 90 ° C. for about 2 hours. This solution was cooled to 28 ° C., 20 g of hydrochloric acid having a concentration of 35% by weight and 115 g of n-butyraldehyde were added thereto, the liquid temperature was lowered to 20 ° C., and this temperature was maintained to carry out an acetalization reaction. The product precipitated out. Thereafter, the liquid temperature was kept at 30 ° C. for 5 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a white powder of a modified polyvinyl acetal resin. When the obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide) and the degree of acetalization was measured using ¹³ C-NMR (nuclear magnetic resonance spectrum), the degree of acetalization was 75 mol%, The amount of hydroxyl groups was 22 mol%.

(Synthesis of (meth) acrylic resin)
In a 2 L separable flask equipped with a stirrer, a cooler, a thermometer, a hot water bath, and a nitrogen gas inlet, 70 parts by weight of methyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd .: Light Ester M), isobutyl methacrylate (manufactured by NOF Corporation: 20 parts by weight of Blemmer IBMA), 10 parts by weight of 2-hydroxyethyl methacrylate (Nippon Yushi Co., Ltd .: Blemmer E), dodecyl mercaptan (made by Wako Pure Chemical Industries) as a chain transfer agent, and ethyl acetate (made by Wako Pure Chemical Industries, Ltd.) as an organic solvent ) 100 parts by weight were mixed to obtain a monomer mixture.

The obtained monomer mixture was bubbled with nitrogen gas for 20 minutes to remove dissolved oxygen, and then the temperature inside the separable flask system was replaced with nitrogen gas and heated until the hot water bath boiled with stirring. A solution obtained by diluting the polymerization initiator with ethyl acetate was added. In addition, a polymerization initiator was added several times during the polymerization.

Seven hours after the start of polymerization, the polymerization was terminated by cooling to room temperature. This obtained the ethyl acetate solution of the (meth) acrylic resin.
100 parts by weight of dihydroterpineol acetate was added to the ethyl acetate solution of the (meth) acrylic resin thus obtained, followed by drying under reduced pressure using an evaporator to volatilize ethyl acetate and perform solvent substitution.

(Preparation of conductive paste)
A dihydroterpineol acetate solution of (meth) acrylic resin and dihydroterpineol acetate are added to the obtained polyvinyl butyral resin, and the resin solid content is 5 weight so that polyvinyl butyral resin: (meth) acrylic resin = 1: 1. % Vehicle was prepared.

Nickel powder (“2020SS” manufactured by Mitsui Kinzoku Co., Ltd.) was blended at a weight ratio of 10:90 with respect to the obtained vehicle, and a conductive paste was prepared by passing three rolls several times.

(Production of ceramic green sheets)
10 parts by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., ESREC B “BM-2” calculated molecular weight 52000) was added to a mixed solvent of 30 parts by weight of toluene and 15 parts by weight of ethanol, and dissolved by stirring. Further, 3 parts by weight of dibutyl phthalate as a plasticizer was added to this resin solution and dissolved by stirring. To the resin solution thus obtained, 100 parts by weight of barium titanate (“BT-03 (average particle size: 0.3 μm)” manufactured by Sakai Chemical Industry Co., Ltd.) as a ceramic powder was added and mixed for 48 hours by a ball mill to produce a ceramic slurry composition. Got.
This slurry composition was applied onto a release-treated polyester film so that the thickness after drying was about 5 μm, air-dried at room temperature for 1 hour, and further heated at 80 ° C. for 3 hours, followed by 120 A ceramic green sheet was obtained by drying at 2 ° C. for 2 hours.

(Printing of conductive paste)
On one side of the obtained green sheet, the prepared conductive paste was printed by a screen printing method so that the thickness after drying was about 2 μm, and dried to form a conductive layer.

(Production of laminate)
The green sheets were cut into 5 cm square, 100 sheets were stacked, and thermocompression bonded at a temperature of 70 ° C. and a pressure of 150 kg / cm ² for 10 minutes to obtain a green sheet laminate.
The obtained green sheet laminate was heated to 400 ° C. at a rate of temperature increase of 3 ° C./min and held for 5 hours in a nitrogen atmosphere, then again heated to 1350 ° C. at a rate of 5 ° C./min to 10 The laminate was obtained by sintering for a period of time.

(Examples 2-18, Comparative Examples 1-15)
A conductive paste and a laminate were produced in the same manner as in Example 1 except that the monomer mixing ratio of the (meth) acrylic resin was changed to the ratio shown in Table 1. In addition, what was described below was used as a monomer.
2-hydroxypropyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd .: light ester HOP), cyclohexyl methacrylate (manufactured by NOF Corporation: CHMA), lauryl methacrylate (manufactured by NOF Corporation: LMA), diethylene glycol monomethacrylate (manufactured by SARTOMER: CD507), polypropylene Glycol monomethacrylate (manufactured by SARTOMER: SR604)

(Examples 19 to 23)
Example 1 except that polyvinyl butyral resin having an ethylene unit content of 0 mol% (Sekisui Chemical Co., Ltd .: BL-S, hydroxyl group content 22 mol%, acetalization degree 74 mol%) was used as the polyvinyl butyral resin. A conductive paste and a laminate were obtained in the same manner as in 6, 9, 15, and 17.

(Examples 24-28)
Example 1 except that polyvinyl butyral resin having an ethylene unit content of 0 mol% (Sekisui Chemical Co., Ltd .: BH-S, hydroxyl group content 22 mol%, acetalization degree 74 mol%) was used as the polyvinyl butyral resin. A conductive paste and a laminate were obtained in the same manner as in 6, 9, 15, and 17.

(Comparative Examples 16-18)
Except not using a polyvinyl butyral resin, it carried out similarly to Example 1, 6, and 9 and obtained the electrically conductive paste and the laminated body.

(Comparative Examples 19-21)
A conductive paste in the same manner as in Examples 1, 6, and 9 except that a polyvinyl butyral resin having a hydroxyl amount of 28 mol% and an acetalization degree of 71 mol% (BL-10 manufactured by Sekisui Chemical Co., Ltd.) was used as the polyvinyl butyral resin. And a laminate was obtained.

(Comparative Examples 22-24)
A conductive paste in the same manner as in Examples 1, 6, and 9 except that a polyvinyl butyral resin having a hydroxyl amount of 36 mol% and an acetalization degree of 63 mol% (BL-1) manufactured by Sekisui Chemical Co., Ltd. was used as the polyvinyl butyral resin. And a laminate was obtained.

(Comparative Example 25)
A conductive paste and a laminate were obtained in the same manner as in Example 1 except that the (meth) acrylic resin was not added.

(Evaluation)
The following evaluation was performed about the (meth) acrylic resin, electrically conductive paste, and laminated body which were obtained by the Example and the comparative example. The results are shown in Tables 1 and 2.

(Weight average molecular weight measurement)
About the acrylic resin obtained by the Example and the comparative example, the weight average molecular weight (Mw) by polystyrene conversion was measured by performing the analysis by a gel permeation chromatography using column LF-804 by SHOKO as a column.

(Evaluation of conductive paste stability)
The conductive pastes obtained in Examples and Comparative Examples were placed in glass bottles and allowed to stand at room temperature for 3 weeks, and the stability of the conductive paste was visually evaluated.
The case where a separation phenomenon in which a transparent layer oozes out on the surface of the conductive paste occurred was evaluated as x.

(Measurement of surface roughness)
About the conductive layer formed in the Example and the comparative example, the centerline average roughness (Ra) of the surface was measured by the method based on JISB0601. Note that a stylus roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 1400D) was used for the measurement.
As a result of the measurement, the case where Ra was 0.3 μm or less was marked as “◯”, the case where it was larger than 0.3 μm and 0.6 μm or less was marked as “Δ”, and the case where it exceeded 0.6 μm was marked as “X”.

(Sinterability evaluation)
The laminates obtained in Examples and Comparative Examples were cooled to room temperature, the center part was cut in the direction perpendicular to the laminate surface, and the sheet state in the vicinity of the 50th layer was observed with an electron microscope. The presence or absence of cracks was confirmed.
The case where there was no crack and the black dot-like material was not confirmed was evaluated as “◯”, and the case where there was a crack or black dot-like material was shown as “X”.

(Evaluation of adhesion (delamination confirmation))
The laminates obtained in the examples and comparative examples were cooled to room temperature, the center part was cut in the direction perpendicular to the laminate surface, and the sheet state in the vicinity of the 50th layer was observed with an electron microscope. The presence or absence of delamination with the conductive layer was observed.
The case where delamination could not be confirmed was marked with ◯, and the case where delamination could be confirmed was marked with X.

According to the present invention, an inorganic powder that is less prone to problems such as sheet attack and delamination, has excellent surface smoothness after coating and drying, has little residual carbon after firing, and can be degreased at low temperatures. A dispersion paste can be provided.

Claims (3)

An inorganic powder dispersion paste containing a polyvinyl acetal resin, a (meth) acrylic resin, an organic solvent having a boiling point of 150 ° C. or higher, and an inorganic powder,
The polyvinyl acetal resin is a polyvinyl acetal resin having a hydroxyl group amount of 25 mol% or less,
The (meth) acrylic resin is a segment derived from methyl methacrylate, a segment derived from a (meth) acrylic monomer having a hydroxyl group, and a (meth) acrylic monomer having 4 to 16 carbon atoms and not containing a hydroxyl group. Inorganic, characterized by containing 15 to 70% by weight of a segment derived from methyl methacrylate and 30% by weight or less of a segment derived from a (meth) acrylic monomer having a hydroxyl group Powder dispersion paste. Having a hydroxyl group (meth) acrylic monomer, according to claim 1, wherein the inorganic Powder dispersed paste, characterized in that it comprises a polyoxyalkylene group. The (meth) acrylic monomer having 4 to 16 carbon atoms and not containing a hydroxyl group is at least one selected from the group consisting of ethyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate. to claim 1 or 2, wherein the inorganic powder dispersed paste.