Polyvinyl acetal resin and resin composition for ceramic green sheet

Abstract

Provided are a polyvinyl acetal resin and a resin composition for a ceramic green sheet, with which it is possible to obtain a ceramic green sheet that has excellent dispersibility and dispersion stability of a ceramic powder, has high strength, and is not susceptible to layering or dimensional change during drying, and with which it is possible to produce a laminated ceramic capacitor that has excellent reliability. The present invention relates to a polyvinyl acetal resin having a Z-average molecular weight (Mz) of from 700000 to 2500000 (inclusive) and a molecular weight differential distribution value of from 5.00 to 110.0 (inclusive) at a LogM of 6.00.

Description

Technical Field

[0001] The present invention relates to a polyvinyl acetal resin and a resin composition for a green sheet of ceramics. Background Art

[0002] In recent years, miniaturization and lamination of electronic components mounted on various electronic devices have been continuously developed, and multilayer circuit boards, laminated coils, laminated ceramic capacitors and other laminated electronic components are widely used.

[0003] Among them, laminated ceramic capacitors are usually manufactured through the following processes.

[0004] First, after adding a plasticizer, a dispersant, etc. to a solution obtained by dissolving a binder resin such as polyvinyl butyral resin or poly(meth)acrylate resin in an organic solvent, ceramic raw material powder is added, and the mixture is uniformly mixed using a mixing device such as a bead mill or a ball mill. After defoaming, a ceramic slurry composition having a certain viscosity is obtained. This slurry composition is cast onto the support surface of a poly(ethylene terephthalate) film or a SUS plate that has been subjected to a demolding treatment using a doctor blade, a reverse roll coater, etc. After heating etc. to distill off volatile components such as the solvent, it is peeled off from the support to obtain a green sheet of ceramics.

[0005] Next, a conductive paste that becomes an internal electrode is coated on the obtained green sheet of ceramics by screen printing, and multiple sheets thus obtained are alternately overlapped and heated and pressed to produce a laminate. Then, a treatment for thermally decomposing and removing the binder resin component etc. contained in the laminate, i.e., a so-called debinding treatment, is performed, and after sintering the external electrode at the end face of the ceramic sintered body obtained by firing, a laminated ceramic capacitor can be obtained.

[0006] The resin composition for a green sheet of ceramics used in the production of a green sheet of ceramics is usually used in the form of a solution in which a polyvinyl acetal resin is dissolved in an organic solvent such as methyl ethyl ketone, toluene, alcohol, and their mixture. However, conventional polyvinyl acetal resins produce a small amount of undissolved matter when dissolved in an organic solvent. If such undissolved matter exists, in the case of being used for a laminated ceramic capacitor, voids are likely to remain in the debinding process and the firing process, or the dispersibility of ceramic powder etc. is reduced, whereby the electrical characteristics of the obtained product are reduced.

[0007] Therefore, when using a polyvinyl acetal resin for the use of a green sheet of ceramics, it is necessary to mix an organic-inorganic compound etc., and after dissolving in an organic solvent, a filtration process is performed to remove the undissolved matter.

[0008] In this regard, Patent Document 1 proposes a polyvinyl acetal resin. When filtering a polyvinyl acetal resin solution prepared by dissolving it in a 1:1 mixed solvent of methyl ethyl ketone and / or toluene and ethanol to form a 5 wt% solution using a filter with a mesh size of 5 μm at a filtration temperature of 25°C and a filtration pressure of 10 mmHg, the reduction rate of the filtration flow rate is less than 10%. In addition, by using such a polyvinyl acetal resin, there are few undissolved substances when dissolved in an organic solvent, the filtration time can be shortened, and thus the productivity can be improved.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-325342 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] On the other hand, in recent years, with the multi-functionalization and miniaturization of electronic devices, larger capacitance and smaller size are required for multilayer ceramic capacitors, and further thinning is required for ceramic green sheets.

[0014] However, when using the polyvinyl acetal resin described in Patent Document 1, there is a problem that the strength of the obtained ceramic green sheet becomes insufficient.

[0015] In addition, in the process of laminating and drying ceramic green sheets, delamination (interlayer peeling) and dimensional changes sometimes occur. If delamination and dimensional changes occur with the thinning of the ceramic green sheet, there is a problem of poor appearance after cutting the laminate.

[0016] An object of the present invention is to provide: a polyvinyl acetal resin and a resin composition for ceramic green sheets that can obtain a ceramic green sheet with excellent dispersibility and dispersion stability of ceramic powder, high strength, and less likely to cause delamination or dimensional changes during drying, and can produce a multilayer ceramic capacitor with excellent reliability.

[0017] Means for Solving the Problems

[0018] The present disclosure (1) relates to a polyvinyl acetal resin having a Z-average molecular weight (Mz) of 700,000 or more and 2,500,000 or less, and a molecular weight differential distribution value at LogM = 6.00 of 5.00 or more and 110.0 or less.

[0019] The present disclosure (2) relates to the polyvinyl acetal resin described in the present disclosure (1), wherein the amount of hydroxyl groups relative to the above Z-average molecular weight (amount of hydroxyl groups / Z-average molecular weight) is 1.30×10 -5 or more.

[0020] The present disclosure (3) relates to a polyvinyl acetal resin described in the present disclosure (1) or (2), and the amount of its acetal groups is 50 to 83 mol%.

[0021] The present disclosure (4) relates to a resin composition for a green sheet of ceramics, which contains the polyvinyl acetal resin described in any one of the present disclosures (1) to (3) and a plasticizer.

[0022] Hereinafter, the present invention will be described in detail.

[0023] The inventors of the present invention have conducted in-depth research and found that: for a polyvinyl acetal resin having a Z-average molecular weight and a molecular weight differential distribution value at LogM = 6.00 within a specified range, a green sheet of ceramics with excellent dispersibility and dispersion stability of ceramic powder, high strength, and less prone to delamination and dimensional change during drying can be obtained, and a multilayer ceramic capacitor with excellent reliability can be fabricated, thus completing the present invention.

[0024] The Z-average molecular weight (Mz) of the polyvinyl acetal resin of the present invention is 700,000 or more and 2,500,000 or less, and the molecular weight differential distribution value at LogM = 6.00 is 5.00 or more and 110.0 or less.

[0025] By containing such a polyvinyl acetal resin, a green sheet of ceramics with high strength and less prone to delamination and dimensional change during drying can be obtained.

[0026] The Z-average molecular weight (Mz) of the polyvinyl acetal resin of the present invention is 700,000 or more and 2,500,000 or less. By setting it within the above range, the wettability with ceramic powder can be improved and the dispersion stability can be enhanced.

[0027] The above Mz is preferably 750,000 or more, more preferably 800,000 or more, preferably 2,400,000 or less, more preferably 2,300,000 or less, and further preferably 1,490,000 or less. That is, the above Z-average molecular weight is 700,000 to 2,500,000, preferably 750,000 to 2,400,000, more preferably 750,000 to 2,300,000, and further preferably 800,000 to 1,490,000.

[0028] The above Mz can be measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and appropriate standards (such as polystyrene standards).

[0029] The molecular weight differential distribution value of the polyvinyl acetal resin of the present invention at LogM = 6.00 is 5.00 or more and 110.0 or less. By setting it within the above range, good balance can be achieved between dispersibility and strength.

[0030] When LogM = 6.00, the differential molecular weight distribution value is preferably 7.00 or more, more preferably 8.00 or more, preferably 100.0 or less, and more preferably 95.0 or less. That is, when LogM = 6.00, the differential molecular weight distribution value is 5.00 to 110.0, preferably 7.00 to 100.0, and more preferably 8.00 to 95.0.

[0031] In the present invention, the "differential molecular weight distribution value at LogM = 6.00" refers to the differential distribution value when the logarithm logM of the molecular weight M is 6.00, and does not merely mean a high molecular weight, but refers to the proportion of high molecular weight components in the resin.

[0032] As an example of the above differential molecular weight distribution value, a differential molecular weight distribution curve with LogM specified on the horizontal axis and the differential molecular weight distribution value specified on the vertical axis is shown in Figure 1 . It should be noted that the above differential molecular weight distribution value is not a detection value obtained by optical measurement, but a value obtained by differentiating the concentration fraction with respect to the logarithm of the molecular weight. In the present invention, it is specified that the differential molecular weight distribution value at LogM = 6.00 is 5.00 or more and 110.0 or less.

[0033] The differential molecular weight distribution value at LogM = 6.00 can be measured by GPC (gel permeation chromatography) on a sample obtained by dissolving the polyvinyl acetal resin to be measured at a concentration of 0.2% by weight in tetrahydrofuran (THF).

[0034] The above Mz and the differential molecular weight distribution value at LogM = 6.00 can be adjusted, for example, by changing the average degree of polymerization, saponification degree of the raw polyvinyl alcohol resin, temperature and time conditions of the acetalization reaction, and appropriately setting the amount of acetal groups, hydroxyl groups, and acetyl groups of the polyvinyl acetal resin.

[0035] In particular, the Mz and the differential molecular weight distribution value at LogM = 6.00 can be adjusted by changing the holding temperature, holding time, heating time, and heating rate during the acetalization reaction described below.

[0036] The polyvinyl acetal resin of the present invention preferably has a structural unit having an acetal group represented by the following formula (1), a structural unit having a hydroxyl group represented by the following formula (2), and a structural unit having an acetyl group represented by the following formula (3).

[0037] [Chemical formula 1]

[0038]

[0039] In the above formula (1), R 1represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0040] In the above formula (1), when R 1 is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, octadecyl, etc. Among them, methyl and n-propyl are preferred.

[0041] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of the structural unit having an acetal group shown in the above formula (1) (hereinafter, also referred to as "acetal group amount") is 50 mol%, and the preferred upper limit is 83 mol%.

[0042] If the above acetal group amount is 50 mol% or more, the solubility in an organic solvent can be improved. If the above acetal group amount is 83 mol% or less, a polyvinyl acetal resin having excellent tensile strength can be produced.

[0043] A more preferred lower limit of the above acetal group amount is 55 mol%, and a more preferred upper limit is 80 mol%. That is, the above acetal group amount is preferably 50 to 83 mol%, and more preferably 55 to 80 mol%.

[0044] The above acetal group amount can be measured, for example, by 1 1H-NMR.

[0045] It should be noted that regarding the calculation method of the acetal group amount, since the acetal group of the polyvinyl acetal resin is obtained by acetalizing two hydroxyl groups of polyvinyl alcohol, a method of counting the two acetalized hydroxyl groups is adopted.

[0046] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of the structural unit having a hydroxyl group shown in the above general formula (2) (hereinafter, also referred to as "hydroxyl group amount") is 18 mol%, and the preferred upper limit is 40 mol%.

[0047] If the above hydroxyl group amount is 18 mol% or more, a polyvinyl acetal resin having high toughness can be produced. If the above hydroxyl group amount is 40 mol% or less, the solubility in an organic solvent can be sufficiently improved.

[0048] A more preferred lower limit of the above hydroxyl group amount is 22 mol%, and a more preferred upper limit is 38 mol%. That is, the above hydroxyl group amount is preferably 18 to 40 mol%, and more preferably 22 to 38 mol%.

[0049] The above hydroxyl group amount can be measured, for example, by 1 1H-NMR.

[0050] In the polyvinyl acetal resin of the present invention, the lower limit of the content of the structural unit having an acetyl group represented by the above general formula (3) (hereinafter, also referred to as "acetyl group amount") is preferably 0.1 mol%, and the upper limit is preferably 22.0 mol%.

[0051] If the above acetyl group amount is 0.1 mol% or more, the high viscosity of the slurry composition for ceramic green sheets caused by the intramolecular and intermolecular hydrogen bonds of the hydroxyl groups in the polyvinyl acetal resin can be suppressed. If the above acetyl group amount is 22.0 mol% or less, the flexibility of the polyvinyl acetal resin will not be excessively increased, and the processability can be improved.

[0052] The more preferable lower limit of the above acetyl group amount is 0.5 mol%, and the more preferable upper limit is 15.0 mol%. That is, the above acetyl group amount is preferably 0.1 to 22.0 mol%, and more preferably 0.5 to 15.0 mol%.

[0053] The above acetyl group amount can be measured, for example, by 1 1H-NMR.

[0054] The hydroxyl group amount relative to the Z-average molecular weight (hydroxyl group amount / Mz) of the polyvinyl acetal resin of the present invention is preferably 1.30×10 -5 or more. By setting it to the above lower limit or more, high dispersibility can be obtained.

[0055] The above hydroxyl group amount / Mz is more preferably 1.40×10 -5 or more, further preferably 1.50×10 -5 or more, preferably 2.70×10 -5 or less, more preferably 2.65×10 -5 or less, further preferably 2.60×10 -5 or less. That is, the above hydroxyl group amount / Mz is preferably 1.30×10 -5 to 2.70×10 -5 , more preferably 1.40×10 -5 to 2.65×10 -5 , further preferably 1.50×10 -5 to 2.60×10 -5 .

[0056] For the polyvinyl acetal resin of the present invention, when a thin film ceramic green sheet is produced, from the viewpoint of maintaining mechanical strength, the preferred lower limit of the average degree of polymerization is 500, and a more preferred lower limit is 600. In addition, from the viewpoint of solubility in organic solvents and dissolution viscosity, the preferred upper limit is 10000, and a more preferred upper limit is 9000. That is, the above average degree of polymerization is preferably 500 to 10000, and more preferably 600 to 9000.

[0057] It should be noted that the average degree of polymerization of the polyvinyl acetal resin is the same as the average degree of polymerization of the raw material polyvinyl alcohol. In addition, the average degree of polymerization can be measured in accordance with JIS K 6726.

[0058] The polyvinyl acetal resin of the present invention can be generally produced by acetalizing a polyvinyl alcohol resin.

[0059] As the polyvinyl alcohol resin, for example, a conventionally known polyvinyl alcohol resin such as a resin produced by saponifying a polyvinyl acetate-based resin with an alkali, an acid, ammonia water, or the like can be used.

[0060] The polyvinyl alcohol resin may be completely saponified, but if at least one unit having two consecutive hydroxyl groups (Japanese original text: 2-linked hydrocarbyl groups) at the meso position and the racemic position is present at least in one part of the main chain, it does not need to be completely saponified and may be a partially saponified polyvinyl alcohol resin. In addition, as the polyvinyl alcohol resin, a copolymer of a monomer copolymerizable with vinyl alcohol such as an ethylene-vinyl alcohol copolymer resin and a partially saponified ethylene-vinyl alcohol copolymer resin and vinyl alcohol may be used.

[0061] Examples of the polyvinyl acetate-based resin include ethylene-vinyl acetate copolymers and the like.

[0062] The polyvinyl alcohol resin preferably has a saponification degree of 75 mol % or more.

[0063] The saponification degree is more preferably 76 mol % or more and 99.4 mol % or less, and further preferably 78 mol % or more and 98 mol % or less. That is, the saponification degree is preferably 76 to 99.4 mol %, and more preferably 78 to 98 mol %.

[0064] By using the above-mentioned polyvinyl alcohol resin, the above-mentioned Mz can be adjusted to be within a predetermined range.

[0065] The acetalization is preferably carried out in an aqueous solvent, in a mixed solvent of water and an organic solvent compatible with water, or in an organic solvent.

[0066] As the organic solvent compatible with water, for example, an alcohol organic solvent can be used.

[0067] Examples of the organic solvent include alcohol organic solvents, aromatic organic solvents, aliphatic ester solvents, ketone solvents, lower alkane solvents, ether solvents, amide solvents, and amine solvents.

[0068] Examples of the alcohol-based organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol.

[0069] Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, and methyl benzoate.

[0070] Examples of the aliphatic ester solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate.

[0071] Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone.

[0072] Examples of the lower alkane solvent include hexane, pentane, octane, cyclohexane, and decane.

[0073] Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether.

[0074] Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetanilide.

[0075] Examples of the amine solvent include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine.

[0076] These solvents may be used as a single component (Japanese original text: monomer) or as a mixture of two or more thereof. Among these solvents, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoint of solubility in the resin and ease of purification.

[0077] The above-mentioned acetalization is preferably carried out in the presence of an acid catalyst.

[0078] The acid catalyst is not particularly limited, and examples thereof include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, carboxylic acids such as formic acid, acetic acid, and propionic acid, and sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. These acid catalysts may be used alone or in combination of two or more compounds. Among them, hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.

[0079] As the aldehyde used in the above acetalization, examples include aldehydes having a linear aliphatic group, a cyclic aliphatic group, or an aromatic group with 1 to 10 carbon atoms. As these aldehydes, those known in the past can be used. The aldehyde used in the above acetalization reaction is not particularly limited, and for example, aliphatic aldehydes, aromatic aldehydes, etc. can be cited.

[0080] As the above aliphatic aldehydes, examples include formaldehyde, acetaldehyde, propionaldehyde, n-butanal, isobutanal, n-pentanal, n-hexanal, 2-ethylbutanal, 2-ethylhexanal, n-heptanal, n-octanal, n-nonanal, n-decanal, valeraldehyde, etc.

[0081] As the above aromatic aldehydes, examples include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde, etc.

[0082] These aldehydes can be used alone or in combination of two or more. As the aldehyde, among them, formaldehyde, acetaldehyde, butyraldehyde, 2-ethylhexanal, and n-nonanal, which have excellent acetalization reactivity and can bring sufficient internal plasticization effect to the resulting resin and can thus impart good flexibility, are preferred. In addition, from the aspect of being able to obtain an adhesive composition with particularly excellent impact resistance and adhesion to metal, formaldehyde, acetaldehyde, and butyraldehyde are more preferred.

[0083] The addition amount of the above aldehyde can be appropriately set according to the amount of acetal groups in the target polyvinyl alcohol acetal resin. In particular, if it is preferably set to 50 mol% or more and 95 mol% or less, more preferably 55 mol% or more and 90 mol% or less, relative to 100 mol% of polyvinyl alcohol, the acetalization reaction proceeds efficiently and unreacted aldehyde is also easily removed, so it is preferred.

[0084] The above acetalization reaction is preferably carried out by raising the temperature at a specified heating rate and then maintaining it under certain time and temperature conditions.

[0085] The heating time in the above acetalization reaction is preferably 120 minutes or more and 420 minutes or less, more preferably 180 minutes or more and 360 minutes or less. That is, the above heating time is preferably 120 to 420 minutes, more preferably 180 to 360 minutes.

[0086] In addition, the above heating rate is preferably 0.1 °C / minute or more and 0.4 °C / minute or less. That is, the above heating rate is preferably 0.1 to 0.4 °C / minute.

[0087] By heating at the above heating time and heating rate, the molecular weight differential distribution value at Mz and LogM = 6.00 can be within a specified range.

[0088] The holding time in the above acetalization reaction is preferably 1 hour or more and 10 hours or less, more preferably 2 hours or more and 9 hours or less, and further preferably 2.6 hours or more. That is, the above holding time is preferably 1 to 10 hours, more preferably 2 to 9 hours. By setting the holding time as above, the above Mz can be set within a specified range.

[0089] The holding temperature in the above acetalization reaction is preferably 30°C or more and 80°C or less, more preferably 40°C or more and 70°C or less. That is, the above holding temperature is preferably 30 to 80°C, more preferably 40 to 70°C. By setting the holding temperature as above, the Mz and the molecular weight differential distribution value at LogM = 6.00 can be within a specified range.

[0090] The resin composition for ceramic green sheets containing the polyvinyl acetal resin and the plasticizer of the present invention is also one of the present inventions.

[0091] The resin composition for ceramic green sheets of the present invention may contain components such as antioxidants, surfactants, ultraviolet absorbers, and defoamers as long as the effects of the present invention are not hindered.

[0092] As a method for manufacturing the resin composition for ceramic green sheets of the present invention, for example, a plasticizer and other additives added as needed can be added to a polyvinyl acetal resin obtained by acetalizing a polyvinyl alcohol resin with an aldehyde and mixed to prepare the resin composition for ceramic green sheets.

[0093] The resin composition for ceramic green sheets of the present invention contains a plasticizer. By adding the above plasticizer, the mechanical strength and flexibility of the obtained ceramic green sheets can be significantly improved.

[0094] Examples of the above plasticizer include: phthalic acid diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, alkylene glycol diesters such as triethylene glycol - bis - 2 - ethylhexanoate, tetraethylene glycol - bis - 2 - ethylhexanoate, triethylene glycol - bis - 2 - ethylbutyrate, tetraethylene glycol - bis - 2 - ethylbutyrate, tetraethylene glycol - bis - heptanoate, and triethylene glycol - bis - heptanoate.

[0095] In the resin composition for ceramic green sheets of the present invention, the preferred lower limit of the content of the above plasticizer relative to 100 parts by weight of the polyvinyl acetal resin is 7 parts by weight, the more preferred lower limit is 8.5 parts by weight, the preferred upper limit is 18 parts by weight, and the more preferred upper limit is 13.5 parts by weight.

[0096] A slurry composition for ceramic green sheets can be prepared by mixing an organic solvent and ceramic powder in the resin composition for ceramic green sheets of the present invention.

[0097] The above-mentioned organic solvents are not particularly limited. For example, as long as they can dissolve the above-mentioned polyvinyl acetal resin, they are not particularly limited. Examples include ketones such as acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone. In addition, examples include alcohols such as methanol, ethanol, isopropyl alcohol, and butanol, aromatic hydrocarbons such as toluene and xylene, etc. Furthermore, examples include esters such as methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, methyl valerate, ethyl valerate, butyl valerate, methyl caproate, ethyl caproate, butyl caproate, 2-ethylhexyl acetate, and 2-ethylhexyl butyrate, etc. In addition, examples include methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, and dihydroterpineol acetate, etc. In particular, from the viewpoints of coatability and drying property, alcohols, ketones, aromatic hydrocarbons, and their mixed solvents are preferred. Among them, a mixed solvent of ethanol and toluene and a mixed solvent of methyl ethyl ketone and toluene are more preferred.

[0098] The content of the above-mentioned organic solvent in the slurry composition for the green ceramic sheet is set according to the type of the polyvinyl acetal resin used, etc., and is not particularly limited. If it is too small, it is difficult to exhibit the solubility required for kneading. In addition, if it is too much, the viscosity of the slurry composition for the green ceramic sheet sometimes becomes too low, and the processability during the production of the green ceramic sheet deteriorates. Therefore, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less.

[0099] Examples of the above-mentioned ceramic powder include powders of metal or non-metal oxides or non-oxides used in the manufacture of ceramics. In addition, the composition of these powders can be a single composition, or powders in a compound state can be used alone or in combination. It should be noted that for the constituent elements of the metal oxides or non-oxides, both the cation and the anion can be formed by a single element, or can be formed by multiple elements, and can also contain additives added to improve the characteristics of the oxides or non-oxides. Specifically, examples include oxides, carbides, nitrides, borides, sulfides, etc. of Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanide elements, actinide elements, Ti, Zr, Hf, Bi, V, Nb, Ta, W, Mn, Fe, Co, Ni, etc.

[0100] In addition, if the specific substances of oxide powders containing multiple metal elements, commonly referred to as composite oxides, are classified according to their crystal structures, examples of substances with a perovskite structure include: NaNbO3, SrZrO3, PbZrO3, SrTiO3, BaZrO3, PbTiO3, BaTiO3, etc. Examples of substances with a spinel structure include MgAl2O4, ZnAl2O4, CoAl2O4, NiAl2O4, MgFe2O4, etc. Examples of substances with an ilmenite structure include MgTiO3, MnTiO3, FeTiO3, etc. Examples of substances with a garnet structure include GdGa5O 12 、Y6Fe5O 12 and so on. Among them, the modified polyvinyl acetal resin of the present application exhibits high characteristics with respect to the green sheet obtained by mixing with BaTiO3 powder.

[0101] The average particle size of the above ceramic powder is not particularly limited. For example, for the production of a thin-layer green sheet (thickness 5 μm or less), it is preferably 0.5 μm or less.

[0102] The slurry composition for the above green sheet may contain other resins such as polyvinyl acetal resins, acrylic resins, and ethyl cellulose other than the polyvinyl acetal resin of the present invention within the range that does not impair the effects of the present invention. In such a case, the content of the polyvinyl acetal resin of the present invention is preferably 50% by weight or more with respect to all binder resins.

[0103] In the slurry composition for the above green sheet, a dispersant, an antioxidant, an ultraviolet absorber, a surfactant, a filler, etc. can be appropriately added as needed, and other resins such as acrylic resins and urethane resins can also be added in small amounts depending on the situation.

[0104] As a method for manufacturing the slurry composition for the above green sheet, there is no particular limitation. For example, there is a method of mixing the polyvinyl acetal resin of the present invention, an organic solvent, a ceramic powder, and various additives added as needed using various mixers such as a ball mill, a mixing mill, and a three-roll mill.

[0105] After coating the slurry composition for the above green sheet, it is dried by heating to obtain a green sheet.

[0106] Using the above green sheet, ceramic electronic components can be manufactured. For example, by performing the process of coating a paste for an electrode layer on the surface of the green sheet and the process of degreasing and firing the laminate obtained by laminating and heat-pressing the green sheet on which the electrode layer is formed, ceramic electronic components can be manufactured.

[0107] As a method for applying the above slurry composition for a green ceramic sheet, there is no particular limitation, and examples thereof include methods using a roll coater, a die coater, a curtain coater, etc. It should be noted that for other specific methods, conventionally well-known methods can be used.

[0108] The above ceramic electronic component is not particularly limited, and examples thereof include: multilayer ceramic capacitors, multilayer ceramic inductors, capacitors, piezoelectric actuators, multilayer varistors, multilayer thermistors, EMI filters, aluminum nitride multilayer substrates, alumina multilayer substrates, etc.

[0109] In the manufacturing method of the above ceramic electronic component, a step of applying a paste for an electrode layer on the surface of the above green ceramic sheet is performed.

[0110] As the paste for the electrode layer, for example, it can be obtained by dissolving a binder resin such as polyvinyl acetal resin, ethyl cellulose, acrylic resin, etc. in an organic solvent and dispersing conductive powder, etc. These resins can be used alone or in combination of two or more. The paste for the electrode layer containing polyvinyl acetal resin shows excellent adhesiveness to the green ceramic sheet in the heat press bonding step, and thus is preferred.

[0111] In the manufacturing method of the above ceramic electronic component, after the above green ceramic sheet formed with the electrode layer is produced, a laminate obtained by laminating and heat press bonding the green ceramic sheets formed with the electrode layer produced in the same manner is degreased and fired, thereby obtaining a multilayer ceramic electronic component that solves problems such as sheet attack and cracks.

[0112] It should be noted that there is no particular limitation on the above heat press bonding step and the steps of degreasing and firing the laminate, and conventionally well-known methods can be used.

[0113] Advantages of the Invention

[0114] According to the present invention, a polyvinyl acetal resin and a resin composition for a green ceramic sheet can be provided, which can obtain a green ceramic sheet with high strength, less likely to delaminate and change in size during drying, and can produce a multilayer ceramic capacitor with excellent reliability.

[0115] In addition, by using the polyvinyl acetal resin of the present invention, the dispersibility and dispersion stability of ceramic powder can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] Figure 1 It is a diagram showing an example of a molecular weight differential distribution curve. DETAILED DESCRIPTION OF THE INVENTION

[0117] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0118] (Example 1)

[0119] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.0 mol %), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 120 g of hydrochloric acid with a concentration of 35 wt % and 140 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.2 °C / min (heating time: 250 minutes). After maintaining the temperature at 70 °C for 3 hours to carry out an acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin.

[0120] (Production of resin composition for ceramic green sheet)

[0121] 1.25 parts by weight of the obtained polyvinyl acetal resin was added to 48.75 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1), and the mixture was stirred and dissolved to obtain a resin composition for a ceramic green sheet.

[0122] (Production of resin sheet)

[0123] The obtained resin composition for a ceramic green sheet was applied to a demolded PET film using a coater so that the dried thickness became 20 μm, and then heated and dried at 70 °C for 60 minutes to produce a resin sheet.

[0124] (Production of slurry composition)

[0125] 2 parts by weight of the obtained polyvinyl acetal resin and 2 parts by weight of dioctyl phthalate (DOP) were added to 96 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1), and the mixture was stirred and dissolved to produce a resin solution.

[0126] In addition, 3 parts by weight of a polyvinyl acetal resin “BL-1” (manufactured by Sekisui Chemical Co., Ltd.) was added to 40 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1), and the mixture was stirred and dissolved. Next, 100 parts by weight of barium titanate powder (BT01, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the mixture was stirred with a bead mill (Ready Mill, manufactured by AIMEX Co., Ltd.) for 180 minutes to produce an inorganic dispersion.

[0127] To 100 parts by weight of the obtained inorganic dispersion, the above resin solution was added, and stirring was carried out using a bead mill, whereby a slurry composition was obtained. It should be noted that during the stirring, sampling was carried out every 5 minutes, and 0.1 part by weight of the obtained slurry composition was added to 10 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1), and stirring was carried out using an ultrasonic disperser (US-303 manufactured by SND Co., Ltd.), whereby a solution for dispersion evaluation was prepared. The particle size distribution was measured using a laser diffraction particle size distribution analyzer (LA-910 manufactured by Horiba, Ltd.), and the stirring was terminated when the D50 value of the particle size distribution reached 1.0 μm.

[0128] (Example 2)

[0129] To 300 g of a polyvinyl alcohol resin (average degree of polymerization 3000, saponification degree 98.9 mol%), 3000 g of pure water was added, and it was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 120 g of hydrochloric acid with a concentration of 35% by weight and 140 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.2 °C / min (heating time 250 minutes), and after maintaining the temperature at 70 °C for 3 hours for an acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0130] (Example 3)

[0131] To 300 g of a polyvinyl alcohol resin (average degree of polymerization 5000, saponification degree 98.9 mol%), 3000 g of pure water was added, and it was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 120 g of hydrochloric acid with a concentration of 35% by weight and 140 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.2 °C / min (heating time 250 minutes), and after maintaining the temperature at 70 °C for 2 hours for an acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0132] (Example 4)

[0133] To 300 g of a polyvinyl alcohol resin (average degree of polymerization 9000, saponification degree 98.9 mol%), 3000 g of pure water was added, and it was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 120 g of hydrochloric acid with a concentration of 35% by weight and 140 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.2 °C / min (heating time 250 minutes), and after maintaining the temperature at 70 °C for 3 hours for an acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0134] (Example 5)

[0135] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 98.8 mol%), 3000 g of pure water was added, and the mixture was stirred at 90°C for about 2 hours to dissolve it. The solution was cooled to 20°C, 120 g of hydrochloric acid with a concentration of 35% by weight and 140 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.16°C / min (heating time: 250 minutes). After maintaining the temperature at 60°C for 3 hours for the acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by conventional methods to obtain a white powder of polyvinyl acetal resin, a resin composition for ceramic green sheet, a resin sheet, and a slurry composition.

[0136] (Example 6)

[0137] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 800, degree of saponification: 98.8 mol%), 3000 g of pure water was added, and the mixture was stirred at 90°C for about 2 hours to dissolve it. The solution was cooled to 20°C, 150 g of hydrochloric acid with a concentration of 35% by weight and 145 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.16°C / min (heating time: 250 minutes). After maintaining the temperature at 60°C for 3 hours for the acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by conventional methods to obtain a white powder of polyvinyl acetal resin, a resin composition for ceramic green sheet, a resin sheet, and a slurry composition.

[0138] (Comparative Example 1)

[0139] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 300, degree of saponification: 99.0 mol%), 3000 g of pure water was added, and the mixture was stirred at 90°C for about 2 hours to dissolve it. The solution was cooled to 20°C, 150 g of hydrochloric acid with a concentration of 35% by weight and 145 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.5°C / min (heating time: 10 minutes). After maintaining the temperature at 25°C for 4 hours for the acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were carried out by conventional methods to obtain a white powder of polyvinyl acetal resin, a resin composition for ceramic green sheet, a resin sheet, and a slurry composition.

[0140] (Comparative Example 2)

[0141] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 500, degree of saponification: 98.5 mol%), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 150 g of hydrochloric acid with a concentration of 35% by weight and 145 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.5 °C / min (heating time: 10 minutes), and the mixture was maintained at 25 °C for 3 hours for an acetalization reaction. After the reaction was completed, neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0142] (Comparative Example 3)

[0143] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 800, degree of saponification: 99.0 mol%), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 150 g of hydrochloric acid with a concentration of 35% by weight and 145 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.7 °C / min (heating time: 7 minutes), and the mixture was maintained at 25 °C for 3 hours for an acetalization reaction. After the reaction was completed, neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0144] (Comparative Example 4)

[0145] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 9000, degree of saponification: 99.0 mol%), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 150 g of hydrochloric acid with a concentration of 35% by weight and 145 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.7 °C / min (heating time: 10 minutes), and the mixture was maintained at 25 °C for 2.5 hours for an acetalization reaction. After the reaction was completed, neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0146] (Comparative Example 5)

[0147] To 300 g of a polyvinyl alcohol resin (average degree of polymerization: 8800, degree of saponification: 99.0 mol%), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve it. The solution was cooled to 20 °C, 150 g of hydrochloric acid with a concentration of 35% by weight and 150 g of n-butyraldehyde were added thereto, and the temperature was raised at a rate of 0.7 °C / min (heating time: 7 minutes), and the mixture was maintained at 25 °C for 2.5 hours for an acetalization reaction. After the reaction was completed, neutralization, washing with water, and drying were carried out by a conventional method to obtain a white powder of a polyvinyl acetal resin, a resin composition for a green ceramic sheet, a resin sheet, and a slurry composition.

[0148] (Comparative Example 6)

[0149] To 300 g of polyvinyl alcohol resin (average degree of polymerization: 800, degree of saponification: 98.7 mol%), 3000 g of pure water was added, and the mixture was stirred at 90 °C for about 2 hours to dissolve. The solution was cooled to 20 °C, and 150 g of hydrochloric acid with a concentration of 35% by weight and 160 g of n-butyraldehyde were added thereto. After maintaining the mixture at 20 °C for 3 hours for acetalization reaction, the reaction was terminated, and neutralization, washing with water, and drying were performed by a conventional method to obtain a white powder of polyvinyl acetal resin, a resin composition for green sheet of ceramic, a resin sheet, and a slurry composition.

[0150] (Evaluation)

[0151] The polyvinyl acetal resins, resin compositions for green sheet of ceramic, resin sheets, and slurry compositions obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[0152] (1) Evaluation of polyvinyl acetal resin

[0153] (1-1) Amount of acetal group, amount of hydroxyl group, amount of acetyl group

[0154] For the obtained polyvinyl acetal resin, 1H-NMR measurement was performed using an AV400 spectrometer (manufactured by Bruker Corporation) to calculate the amount of acetal group, the amount of hydroxyl group, and the amount of acetyl group. 1 The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 1.6% by weight to prepare a measurement solution. In addition, 1H-NMR measurement was performed at 80 °C.

[0155] It should be noted that the obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 1.6% by weight to prepare a measurement solution. In addition, 1H-NMR measurement was performed at 80 °C. 1 1H-NMR measurement was performed at 80 °C.

[0156] (1-2) Mz, molecular weight differential distribution value at LogM = 6.00

[0157] The obtained polyvinyl acetal resin was dissolved in tetrahydrofuran (THF) at a concentration of 0.2% by weight, and measurement was performed using a GPC device HLC-8220 (manufactured by Tosoh Corporation). From the obtained measurement results, the Z-average molecular weight Mz was calculated using a molecular weight calibration curve prepared with a monodisperse polystyrene standard sample.

[0158] In addition, the molecular weight differential distribution value at LogM = 6.00 was measured from the obtained molecular weight differential distribution curve.

[0159] It should be noted that TSKgel SuperHZ (manufactured by Tosoh Corporation) was used as the column.

[0160] (2) Evaluation of resin sheet

[0161] (2-1) Tensile elastic modulus, elongation at break, and stress at break

[0162] For the obtained resin sheet, in accordance with JIS K 7113, using a tensile testing machine (manufactured by Shimadzu Corporation, AUTOGRAPH AGS-J), the stress at break (MPa), elongation at break (%), and tensile elastic modulus (MPa) were measured under the condition of a tensile speed of 20 mm / min.

[0163] (3) Evaluation of the slurry composition

[0164] (3-1) Dispersibility

[0165] (Preparation of the dispersibility evaluation solution)

[0166] 0.1 part by weight of the obtained slurry composition was added to 10 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1), and stirred using an ultrasonic disperser (manufactured by SND Corporation, US-303) to prepare a dispersibility evaluation solution.

[0167] (Dispersibility evaluation)

[0168] For the obtained dispersibility evaluation solution, the particle size distribution was measured 60 minutes after the end of stirring.

[0169] It should be noted that the particle size distribution was measured using a laser diffraction particle size distribution analyzer (LA-910 manufactured by Horiba, Ltd.), and the average particle size was measured.

[0170] (3-2) Dispersion stability

[0171] Using the dispersibility evaluation solution obtained in the above (3-1), the particle size distribution was measured after standing at 23°C for 1 week, and the average particle size was measured.

[0172] (4) Evaluation of the green ceramic sheet

[0173] (Preparation of the green ceramic sheet)

[0174] The obtained slurry composition was coated on a PET film subjected to a release treatment using a coater so that the dried thickness became 20 μm, and then heated and dried to prepare a green ceramic sheet.

[0175] (4-1) Tensile elastic modulus, elongation at break, and stress at break

[0176] (Preparation of the green ceramic sheet)

[0177] 1 part by weight of polyvinyl acetal resin (manufactured by Sekisui Chemical Co., Ltd., BL-1) was added to a mixed solvent of 20 parts by weight of toluene and 20 parts by weight of ethanol, and stirred until dissolved. Next, 100 parts by weight of barium titanate powder (manufactured by Sakai Chemical Industry Co., Ltd., BT01, average particle diameter 0.1 μm) was added to the obtained solution, and stirred with a bead mill (ReadyMill manufactured by AIMEX Co., Ltd.) for 180 minutes to prepare an inorganic dispersion.

[0178] The resin composition for green ceramic sheets obtained in the examples and comparative examples was added to the obtained inorganic dispersion, stirred with a bead mill for 90 minutes, and then coated on a demolded PET film using a coater so that the thickness after drying was 20 μm. Then, it was heated and dried at 40 °C for 30 minutes, and the PET film was peeled off to prepare a green ceramic sheet.

[0179] For the obtained green ceramic sheets, according to JIS K 7113, using a tensile testing machine (AUTOGRAPH AGS-J manufactured by Shimadzu Corporation), the breaking point stress (MPa), tensile elastic modulus (MPa), and breaking point elongation (%) were measured under the condition of a tensile speed of 20 mm / min.

[0180] (4-2) Cut cross-section state

[0181] The fracture surface after the measurement of "(4-1) Tensile elastic modulus, breaking point elongation, and breaking point stress" was observed by SEM and judged according to the following evaluation criteria.

[0182] ◎: The fracture surface has no defects, cracks, or scratches

[0183] ○: The fracture surface has no defects or cracks, but has damage

[0184] △: The fracture surface has no defects, but has cracks

[0185] ×: The fracture surface has defects and interlaminar peeling

[0186] (4-3) Dimensional change rate

[0187] Green ceramic sheets were prepared by the same method as in "(4-1) Tensile elastic modulus, breaking point elongation, and breaking point stress". The obtained green ceramic sheets were dried at 70 °C for 3 hours, and the dimensional change rate before and after drying at 70 °C was calculated and evaluated according to the following criteria.

[0188] ◎: 2% or less

[0189] ○: More than 2% and 3% or less

[0190] △: More than 3% and 4% or less

[0191] ×: More than 4%

[0192] [Table 1]

[0193]

[0194] Industrial availability

[0195] According to the present invention, it is possible to provide: a polyvinyl acetal resin and a resin composition for a green sheet of ceramics, which can obtain a green sheet of ceramics having excellent dispersibility and dispersion stability of ceramic powder, high strength, and less likely to cause delamination or dimensional change during drying, and can produce a multilayer ceramic capacitor with excellent reliability.

Claims

1. A polyvinyl acetal resin having a Z average molecular weight Mz of 700,000 or more and 2,500,000 or less, The molecular weight differential distribution value when LogM=6.00 is 5.00 or more and 110.0 or less.

2. The polyvinyl acetal resin according to claim 1, wherein The amount of hydroxyl groups relative to the Z average molecular weight, that is, the amount of hydroxyl groups / Z average molecular weight, is 1.30×10 -5 above. 3 . The polyvinyl acetal resin according to claim 1 , wherein the acetal group content is 50 mol % to 83 mol %. 4 . A resin composition for a ceramic green sheet, comprising the polyvinyl acetal resin according to claim 1 or 2 and a plasticizer.

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