Polyvinyl acetal resin

Abstract

The present invention provides: a polyvinyl acetal resin that makes it possible to obtain a ceramic green sheet that has high mechanical strength and a suitable surface roughness and to produce a layered ceramic capacitor that has excellent reliability; a ceramic green sheet slurry; a ceramic green sheet; and a layered ceramic capacitor. The present invention is a polyvinyl acetal resin for which the Z-average molecular weight (THFMz) and the Z-average molecular weight (NMPMz) obtained by GPC that uses a differential refractometer using THF and NMP as a mobile phase, respectively, satisfy expression (1) and for which the hydroxyl group content–based wavenumber width found from expression (2) is 8.3–9.4, where A is the wavenumber on the low wavenumber side and B is the wavenumber on the high wavenumber side of the wavenumbers at the transmittance a (%) that satisfies (100-(100-X) / 2), where X (%) is the minimum transmittance for the peaks within a wavenumber range of 3050–3750 cm-1 on an IR absorption spectrum obtained using an infrared spectrophotometer, and the hydroxyl group content is measured by 1H-NMR. (1) THFMz-NMPMz<470000. (2) Hydroxyl group content–based wavenumber width (cm-1 / mol%)=((B-A) / hydroxyl group content).

Description

Polyvinyl acetal resin

[0001] The present invention relates to a polyvinyl acetal resin, a slurry for a ceramic green sheet, a ceramic green sheet, and a multilayer ceramic capacitor.

[0002] In recent years, electronic components mounted in various electronic devices have become increasingly miniaturized and multilayered, resulting in widespread use of multilayer electronic components such as multilayer circuit boards, laminated coils, and multilayer ceramic capacitors. Multilayer ceramic capacitors, among others, are generally manufactured through the following process. First, a plasticizer, dispersant, etc. are added to a solution of a binder resin, such as polyvinyl butyral resin or poly(meth)acrylate resin, dissolved in an organic solvent. Then, ceramic raw material powder is added and uniformly mixed using a mixing device such as a bead mill or ball mill. After degassing, a ceramic slurry composition with a constant viscosity is obtained. This slurry composition is cast onto a support surface, such as a release-treated polyethylene terephthalate film or SUS plate, using a doctor blade or reverse roll coater. The resulting ceramic green sheets are then heated to remove volatiles such as the solvent, and the sheets are peeled off from the support to obtain ceramic green sheets. Next, multiple sheets of the resulting ceramic green sheets, each coated with a conductive paste for internal electrodes by screen printing, are alternately stacked and heated and pressed together to form a laminate. Thereafter, the laminate is subjected to a process of thermally decomposing and removing binder resin components and the like contained in the laminate, a so-called degreasing process, and then external electrodes are sintered onto the end faces of the ceramic sintered body obtained by firing, to obtain a multilayer ceramic capacitor.

[0003] For example, Patent Document 1 describes a polyvinyl acetal resin suitable as a ceramic binder, which has a predetermined degree of polymerization, vinyl ester unit content, and degree of acetalization, and in which the molar ratio of the portion acetalized with acetaldehyde to the portion acetalized with butylaldehyde is within a predetermined range. Also, Patent Document 2 describes a polyvinyl acetal resin having a predetermined degree of polymerization, vinyl ester unit content, and degree of acetalization, and having specific structural units.

[0004] JP 2011-236304 A International Publication No. 2012 / 023517

[0005] On the other hand, in recent years, with the trend toward multifunctionalization and miniaturization of electronic devices, multilayer ceramic capacitors are required to have larger capacitance and be smaller, and ceramic green sheets are also required to be thinner. However, when the polyvinyl acetal resins described in Patent Documents 1 and 2 are used, there is a problem that the strength of the obtained ceramic green sheets is insufficient. There is also a problem that the surface roughness of the obtained ceramic green sheets is reduced.

[0006] An object of the present invention is to provide a polyvinyl acetal resin that can produce ceramic green sheets having high mechanical strength and suitable surface roughness, and that can be used to fabricate highly reliable multilayer ceramic capacitors; and to provide a ceramic green sheet slurry, a ceramic green sheet, and a multilayer ceramic capacitor that use the polyvinyl acetal resin.

[0007] The present disclosure 1 relates to a polymer having a z-average molecular weight (THFMz) obtained by using THF as a mobile phase in GPC measurement with a differential refractive index detector, and a z-average molecular weight (NMPMz) obtained by using NMP as a mobile phase, which satisfy the following formula (1): －１ When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B, １ The polyvinyl acetal resin has a hydroxyl group amount equivalent wavenumber width of 8.3 to 9.4, calculated by the following formula (2) using the amount of hydroxyl groups measured by H-NMR: THFMz-NMPMz<470000 (1) Hydroxyl group amount equivalent wavenumber width (cm －１ / mol%) = [(B - A) / amount of hydroxyl groups] (2) In the present disclosure 2, －１ Above, 3415cm －１ The polyvinyl acetal resin according to Disclosure 1 is as follows: Disclosure 3 is the polyvinyl acetal resin according to Disclosure 1, which is as follows: １The polyvinyl acetal resin according to Disclosure 1 or 2 has a hydroxyl group-acetal group amount-equivalent wavenumber width of 0.120 to 0.135, calculated by the following formula (3) using the hydroxyl group amount and acetal group amount measured by H-NMR. －１ / mol% / mol%) = [(B-A) / amount of hydroxyl groups / amount of acetal groups] (3) Disclosure 4 is the polyvinyl acetal resin according to any one of Disclosures 1 to 3, wherein a 5% by mass solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 64 mPa·s or more and 2000 mPa·s or less when measured using a Brookfield viscometer at a solution temperature of 20°C. Disclosure 5 is the polyvinyl acetal resin according to any one of Disclosures 1 to 4, wherein the amount of hydroxyl groups is 18 mol% or more and 40 mol% or less. Disclosure 6 is the polyvinyl acetal resin according to any one of Disclosures 1 to 5, wherein the amount of acetyl groups is 0.1 mol% or more and 20 mol% or less. Disclosure 7 is a slurry for a ceramic green sheet, comprising the polyvinyl acetal resin according to any one of Disclosures 1 to 6, an organic solvent, and a ceramic powder. Disclosure 8 is a ceramic green sheet obtained using the ceramic green sheet slurry described in Disclosure 7. Disclosure 9 is a multilayer ceramic capacitor obtained using the ceramic green sheet described in Disclosure 8. The present invention will be described in detail below.

[0008] As a result of extensive research, the present inventors have found that the z-average molecular weight measured by changing the solvent of the mobile phase satisfies a predetermined relationship, and the IR absorption spectrum measured by an infrared spectrophotometer has a peak of 3050 to 3750 cm －１ The inventors have found that a polyvinyl acetal resin having a peak wavenumber width within a predetermined range has high mechanical strength, can provide a ceramic green sheet with a suitable surface roughness, and can fabricate a multilayer ceramic capacitor with excellent reliability, and have completed the present invention.

[0009] The polyvinyl acetal resin of the present invention has a z-average molecular weight (THFMz) obtained by GPC measurement using a differential refractive index detector, using THF as a mobile phase, and a z-average molecular weight (NMPMz) obtained by using NMP as a mobile phase, which satisfy the following formula (1): －１ When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B, １ Using the amount of hydroxyl groups measured by H-NMR, the hydroxyl group amount equivalent wavenumber width calculated by the following formula (2) is 8.3 to 9.4. THFMz-NMPMz<470000 (1) Hydroxyl group amount equivalent wavenumber width (cm －１ / mol%)=[(B−A) / amount of hydroxyl groups] (2) By using such a polyvinyl acetal resin, it is possible to obtain a ceramic green sheet having high strength and suitable surface roughness.

[0010] The polyvinyl acetal resin of the present invention has a z-average molecular weight (THFMz) and a z-average molecular weight (NMPMz) that satisfy the above formula (1) when measured by GPC using a differential refractive index detector. By ensuring that the molecular weight falls within the above range, the molecular weight variation can be narrowed, thereby reducing the surface roughness of the ceramic green sheet. The THFMz-NMPMz is preferably 100 or more, more preferably 1,000 or more, and is preferably less than 470,000, more preferably less than 450,000. In the present invention, THFMz-NMPMz serves as an indicator of the narrowness of the apparent molecular weight variation due to hydrogen bonding. The THFMz-NMPMz can be calculated by measuring the z-average molecular weight (THFMz) obtained by gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase and solvent and a refractive index detector as the detector, using THF as the mobile phase, and then measuring the z-average molecular weight (NMPMz) obtained by GPC using N-methylpyrrolidone as the mobile phase and solvent and a refractive index detector as the detector, using NMP as the mobile phase, and then calculating the THFMz-NMPMz. A column such as TSKgel Super HZM-H (manufactured by Tosoh Corporation) can be used to measure the THFMz, and a column such as LF-804 (manufactured by Shodex) can be used to measure the NMPMz.

[0011] The polyvinyl acetal resin of the present invention preferably has a z-average molecular weight (THFMz) of 300,000 or more and 2,000,000 or less when obtained using THF as a mobile phase. By setting the THFMz within this range, it is possible to suppress variations in strength of the ceramic green sheet. The THFMz is more preferably 400,000 or more and more preferably 1,200,000 or less.

[0012] The polyvinyl acetal resin of the present invention preferably has a z-average molecular weight (NMPMz) obtained using NMP as a mobile phase of 300,000 or more and 1,500,000 or less. By setting the NMPMz within this range, variation in the ceramic green sheet can be suppressed. The NMPMz is more preferably 400,000 or more and more preferably 1,000,000 or less.

[0013] The THFMz-NMPMz can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, amount of hydroxyl groups, amount of acetyl groups, etc. of the polyvinyl acetal resin. In particular, the THFMz-NMPMz can be adjusted by changing the cooling temperature, cooling time, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and can also be adjusted by changing the reaction temperature, reaction time, temperature rise rate, cooling temperature, cooling time, and cooling rate, and can be adjusted particularly by changing the reaction temperature and reaction time.

[0014] The polyvinyl acetal resin of the present invention has an IR absorption spectrum measured by an infrared spectrophotometer, and has a wave number of 3050 to 3750 cm －１ When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B, １The hydroxyl group amount-equivalent wavenumber width calculated by the above formula (2) using the hydroxyl group amount measured by H-NMR is 8.3 to 9.4. By setting the wavenumber width within this range, the strength of the ceramic green sheet can be improved. The preferred lower limit of the wavenumber width is 8.32, more preferably 8.35, and even more preferably 8.38, and the preferred upper limit is 9.38, more preferably 9.35, and even more preferably 9.33. In the present invention, the wavenumber width serves as an indicator of the amount of hydrogen bonding between resins. The IR absorption spectrum can be measured by a transmission method using a Fourier transform infrared spectrophotometer (such as the FT-720 manufactured by HORIBA or the FT / IR-4000 manufactured by JASCO) at 20°C, for example.

[0015] The polyvinyl acetal resin of the present invention is １ The hydroxyl group-acetal group amount-equivalent wavenumber width calculated by the above formula (3) using the hydroxyl group amount and acetal group amount measured by H-NMR is preferably 0.10 to 0.150, and more preferably 0.120 to 0.135. By setting the wavenumber width within the above range, the strength of the ceramic green sheet can be improved. The lower limit of the hydroxyl group-acetal group amount-equivalent wavenumber width is more preferably 0.122, even more preferably 0.123, and the upper limit is more preferably 0.134, even more preferably 0.133.

[0016] In the analysis of the polyvinyl acetal resin using the infrared spectrophotometer, a spectrum derived from the stretching vibration of the C—H bond of the polyvinyl acetal resin was observed at 2980 cm －１ The above peak analysis firstly revealed that the minimum transmittance of the peak due to the stretching vibration of the C-H bond is around 2500 cm －１ and 3050 cm －１ The film thickness of the measurement sample is adjusted so that it is 20% of the baseline when the line connecting the lines is connected. －１ A baseline is drawn for the peaks that appear within this range, and the data is corrected so that the transmittance at both ends of the peak is 100%.

[0017] An example of the IR absorption spectrum of the polyvinyl acetal resin of the present invention measured by an infrared spectrophotometer at 20°C is shown in Figure 1. In Figure 1, the vertical axis represents transmittance and the horizontal axis represents wavenumber. In the IR absorption spectrum shown in Figure 1, the minimum transmittance X is 65.7%. The transmittance a satisfying [100-(100-X) / 2] is 82.85%, and the wavenumber A on the low wavenumber side is 3297 cm. －１ , the wave number B on the high wave number side is 3557 cm －１ In the above case, if the amount of hydroxyl groups is 30 mol%, the wavenumber width converted into the amount of hydroxyl groups [(B−A) / amount of hydroxyl groups] is 8.67 (cm －１ / mol%). The wave number A is 3220 cm －１ More than 3275 cm is preferable. －１ More preferably, 3280 cm or more －１ More preferably, it is 3415 cm or more. －１ The following is preferred: －１ More preferably, 3300 cm or less －１ More preferably, the wave number B is 3530 cm or less. －１ More than 3550 cm －１ More preferably, 3600 cm －１ Preferably, 3580 cm or less －１ The following is more preferable: The transmittance a is preferably 80% or more and 85% or less.

[0018] The wavenumber width can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, amount of hydroxyl groups, amount of acetyl groups, etc. of the polyvinyl acetal resin. The wavenumber width can be adjusted by changing the cooling temperature, cooling time, cooling rate, heating rate, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and can also be adjusted by changing the reaction temperature, reaction time, heating rate, cooling temperature, cooling time, and cooling rate, and can be adjusted particularly by changing the cooling temperature and cooling time.

[0019] The polyvinyl acetal resin of the present invention preferably has a solution viscosity of 64 mPa·s or more and 2000 mPa·s or less when a 5% by mass solution dissolved in a 1:1 mixed solvent of ethanol and toluene is measured using a Brookfield viscometer at a solution temperature of 20°C. From the viewpoint of improving tensile strength, the viscosity is more preferably 64 mPa·s or more, and even more preferably 65 mPa·s or more. From the viewpoint of improving the viscosity stability of the ceramic slurry composition, the viscosity is more preferably 2000 mPa·s or less, and even more preferably 1800 mPa·s or less. As the Brookfield viscometer, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. can be used. Furthermore, the rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the solution viscosity. For example, it is preferable to measure using SPINDLE Nos. M1 to M4 at a rotation speed in the range of 0.3 to 100 rpm.

[0020] The viscosity can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, hydroxyl groups, acetyl groups, etc. of the polyvinyl acetal resin.

[0021] The polyvinyl acetal resin of the present invention preferably has a structural unit having an acetal group represented by the following formula (4), a structural unit having a hydroxyl group represented by the following formula (5), and a structural unit having an acetyl group represented by the following formula (6).

[0022] In the above formula (4), R １ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0023] In the above formula (4), R １is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, an octadecyl group, etc. Of these, a methyl group and an n-propyl group are preferred.

[0024] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetal group represented by the above formula (4) (hereinafter also referred to as the "acetal group amount") is preferably 50 mol% at the lower limit and 83 mol% at the upper limit. When the acetal group amount is 50 mol% or more, the solubility in organic solvents can be improved. When the acetal group amount is 83 mol% or less, the polyvinyl acetal resin can have excellent tensile strength. The lower limit of the acetal group amount is more preferably 55 mol%, even more preferably 58 mol%, and even more preferably 80 mol%, and even more preferably 78 mol%. That is, the acetal group amount is preferably 50 to 83 mol%, more preferably 55 to 80 mol%, and even more preferably 58 to 78 mol%. By setting the hydroxyl group amount above, the hydroxyl group amount-acetal group amount converted wavenumber width can be set within a predetermined range. The acetal group amount can be, for example, １ The amount of acetal groups can be measured by H-NMR. Since the acetal groups of the polyvinyl acetal resin are obtained by acetalizing two hydroxyl groups of polyvinyl alcohol, the amount of acetal groups is calculated by counting the two acetalized hydroxyl groups.

[0025] In the polyvinyl acetal resin of the present invention, the content of the hydroxyl group-containing structural unit represented by the general formula (5) (hereinafter also referred to as the "hydroxyl group amount") is preferably 18 mol% at the lower limit and 40 mol% at the upper limit. When the hydroxyl group amount is 18 mol% or more, the polyvinyl acetal resin can have high toughness. When the hydroxyl group amount is 40 mol% or less, the solubility in organic solvents can be sufficiently improved. The hydroxyl group amount has a more preferred lower limit of 20 mol%, an even more preferred lower limit of 22 mol%, and a more preferred upper limit of 38 mol%, and an even more preferred upper limit of 36 mol%. That is, the hydroxyl group amount is preferably 18 to 40 mol%, more preferably 20 to 38 mol%, and even more preferably 22 to 36 mol%. By setting the hydroxyl group amount in the above range, the hydroxyl group amount equivalent wavenumber width and the hydroxyl group amount / acetal group amount equivalent wavenumber width can be set within a predetermined range. The hydroxyl group amount can be, for example, １ It can be measured by H-NMR.

[0026] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetyl group represented by the general formula (6) (hereinafter also referred to as the "acetyl group amount") is preferably 0.1 mol% at the lower limit and 20.0 mol% at the upper limit. When the acetyl group amount is 0.1 mol% or more, it is possible to suppress the increase in viscosity of the slurry composition for a ceramic green sheet due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin. When the acetyl group amount is 20.0 mol% or less, it is possible to improve the handleability of the polyvinyl acetal resin without excessively increasing its flexibility. The acetyl group amount is more preferably 0.5 mol% at the lower limit and 18.0 mol% at the upper limit. That is, the acetyl group amount is preferably 0.1 to 20.0 mol%, and more preferably 0.5 to 18.0 mol%. The acetyl group amount may be, for example, １ It can be measured by H-NMR.

[0027] The polyvinyl acetal resin of the present invention has an average degree of polymerization of preferably 500 or more preferably 600, from the viewpoint of maintaining mechanical strength when producing a thin film ceramic green sheet. Furthermore, from the viewpoint of solubility in organic solvents and dissolution viscosity, the average degree of polymerization is preferably 10,000 or more preferably 9,000. That is, the average degree of polymerization is preferably 500 to 10,000, more preferably 600 to 9,000. The average degree of polymerization of the polyvinyl acetal resin is the same as that of the raw material polyvinyl alcohol. The average degree of polymerization can be measured in accordance with JIS K 6726.

[0028] The polyvinyl acetal resin of the present invention can usually be produced by acetalizing a polyvinyl alcohol resin.

[0029] The polyvinyl alcohol resin can be, for example, a conventionally known polyvinyl alcohol resin, such as a resin produced by saponifying a polyvinyl acetate resin with an alkali, an acid, aqueous ammonia, or the like. The polyvinyl alcohol resin can be fully saponified, but it does not need to be fully saponified as long as it has at least one unit having two consecutive hydroxyl groups at the meso and racemo positions at at least one location on the main chain; it can also be a partially saponified polyvinyl alcohol resin. Furthermore, the polyvinyl alcohol resin can also be a copolymer of vinyl alcohol and a monomer copolymerizable with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin. Examples of the polyvinyl acetate resin include ethylene-vinyl acetate copolymers.

[0030] The polyvinyl alcohol resin preferably has a degree of saponification of 75 mol% or more, more preferably 76 mol% or more and 99.9 mol% or less, and even more preferably 78 mol% or more and 99.5 mol% or less. That is, the degree of saponification is preferably 76 to 99.9 mol%, and more preferably 78 to 99.5 mol%.

[0031] The acetalization is preferably carried out in an aqueous solvent, a mixed solvent of water and a water-compatible organic solvent, or an organic solvent. Examples of the water-compatible organic solvent include alcohol-based organic solvents. Examples of the organic solvent include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffin-based solvents, ether-based solvents, amide-based solvents, and amine-based solvents. Examples of the alcohol-based organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol. Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, and methyl benzoate. Examples of the aliphatic ester-based solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate. Examples of the ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone. Examples of the lower paraffin solvents include hexane, pentane, octane, cyclohexane, and decane. Examples of the ether solvents include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether. Examples of the amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetanilide. Examples of the amine solvents include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine. These solvents can be used alone or in combination of two or more. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoints of solubility in the resin and ease of purification.

[0032] The acetalization is preferably carried out in the presence of an acid catalyst. 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 paratoluenesulfonic acid. These acid catalysts may be used alone or in combination of two or more compounds. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.

[0033] Examples of the aldehyde used in the acetalization include aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Conventionally known aldehydes can be used as these aldehydes. The aldehyde used in the acetalization reaction is not particularly limited, and examples include aliphatic aldehydes and aromatic aldehydes. Examples of the aliphatic aldehyde include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, and amylaldehyde. Examples of the aromatic aldehyde include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used alone or in combination of two or more. Among these, preferred aldehydes are formaldehyde, acetaldehyde, butylaldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde, which have excellent acetalization reactivity and can provide a sufficient internal plasticizing effect to the resulting resin, thereby imparting good flexibility. Furthermore, formaldehyde, acetaldehyde, and butylaldehyde are more preferred because they can provide an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.

[0034] The amount of the aldehyde to be added can be appropriately determined depending on the amount of acetal groups in the target polyvinyl acetal resin. In particular, it is preferable to add the aldehyde in an amount of from 50 mol % to 95 mol %, more preferably from 55 mol % to 90 mol %, based on 100 mol % of polyvinyl alcohol, because this allows the acetalization reaction to proceed efficiently and makes it easy to remove unreacted aldehyde.

[0035] The acetalization reaction is preferably carried out by lowering the temperature to a predetermined temperature and maintaining it thereat (cooling step), and then raising the temperature to a predetermined temperature and maintaining it thereat (reaction step). The cooling time in the cooling step is preferably 30 minutes to 5 hours, more preferably 50 minutes to 4 hours, and even more preferably 1 hour to 3 hours. The cooling temperature in the cooling step is more preferably 6°C to 22°C, more preferably 8°C to 20°C, and even more preferably 10°C to 17°C. The cooling rate is preferably 0.2°C / min to 3°C / min, and more preferably 0.5°C / min to 2°C / min. By setting the cooling time, cooling temperature, and cooling rate as described above, the wavenumber width can be set within a predetermined range.

[0036] The reaction time in the reaction step is preferably 30 minutes or more and 12 hours or less, more preferably 1 hour or more and 10 hours or less, and even more preferably 2 hours or more and 6 hours or less. The reaction temperature in the reaction step is preferably 47°C or more and 58°C or less, and more preferably 50°C or more and 55°C or less. The temperature rise rate is preferably 0.05°C or more and 1.5°C / min or less, and more preferably 0.1°C or more and 1°C / min or less. By setting the reaction time, reaction temperature, and temperature rise rate as described above, the THFMz-NMPMz can be adjusted to a predetermined range.

[0037] The polyvinyl acetal resin of the present invention and a plasticizer can be used to form a resin composition for a ceramic green sheet. The resin composition for a ceramic green sheet may contain other components such as an antioxidant, a surfactant, an ultraviolet absorber, and an antifoaming agent, as long as the effects of the present invention are not impaired.

[0038] As a method for producing the resin composition for a ceramic green sheet, for example, a plasticizer and other additives that are added as needed can be added to a polyvinyl acetal resin obtained by acetalizing a polyvinyl alcohol resin with an aldehyde, and then mixed to obtain a resin composition for a ceramic green sheet.

[0039] The resin composition for ceramic green sheets contains a plasticizer. Addition of the plasticizer can significantly improve the mechanical strength and flexibility of the resulting ceramic green sheets. Examples of the plasticizer include phthalate diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, and alkylene glycol diesters such as triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0040] In the resin composition for a ceramic green sheet, the content of the plasticizer relative to 100 parts by weight of the polyvinyl acetal resin is preferably 7 parts by weight in lower limit, more preferably 8.5 parts by weight in lower limit, and preferably 18 parts by weight in upper limit, more preferably 13.5 parts by weight in upper limit.

[0041] A slurry for ceramic green sheets can be prepared by mixing the polyvinyl acetal resin of the present invention with an organic solvent and ceramic powder.

[0042] The organic solvent is not particularly limited as long as it can dissolve the polyvinyl acetal resin, and examples thereof include ketones such as acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone. Other examples include alcohols such as methanol, ethanol, isopropanol, and butanol, and aromatic hydrocarbons such as toluene and xylene. Further examples include esters such as methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, and 2-ethylhexyl butyrate. Other examples include methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, and dihydroterpineol acetate. In particular, alcohols, ketones, aromatic hydrocarbons and mixed solvents thereof are preferred in terms of coating and drying properties, with a mixed solvent of ethanol and toluene and a mixed solvent of methyl ethyl ketone and toluene being more preferred.

[0043] The content of the organic solvent in the ceramic green sheet slurry is determined depending on the type of polyvinyl acetal resin used and is not particularly limited, but if it is too low, the solubility required for kneading is difficult to exhibit. On the other hand, if it is too high, the viscosity of the ceramic green sheet slurry composition becomes too low, which can result in poor handling when producing ceramic green sheets. Therefore, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less.

[0044] Examples of the ceramic powder include powders of metal or nonmetal oxides or non-oxides used in ceramic production. These powders may be single compositions, compounds, or mixtures. The constituent elements of the metal oxides or non-oxides, both cations and anions, may be single elements or multiple elements, and may further contain additives added to improve the properties of the oxides or non-oxides. Specific examples include oxides, carbides, nitrides, borides, sulfides, etc. of Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanides, actinides, Ti, Zr, Hf, Bi, V, Nb, Ta, W, Mn, Fe, Co, Ni, etc. Specific examples of oxide powders containing multiple metal elements, commonly referred to as double oxides, can be classified based on their crystal structure, such as NaNbO, which has a perovskite structure. ３ , SrZrO ３ , PbZrO ３ , SrTiO ３ , BaZrO ３ , PbTiO ３ , BaTiO ３ Examples of materials that have a spinel structure include MgAl ２ O ４ , ZnAl ２ O ４ , CoAl ２ O ４ , NiAl ２ O4, MgFe ２ O ４ Examples of materials with an ilmenite structure include MgTiO ３ , MnTiO ３ , FeTiO ３ As a material having a garnet structure, GdGa ５ O １２ , Y ６ Fe ５ O １２ Among these, the modified polyvinyl acetal resin of the present invention is BaTiO ３ It exhibits high properties compared to ceramic green sheets mixed with powder.

[0045] The average particle size of the ceramic powder is not particularly limited, but for example, for producing a thin ceramic green sheet (thickness of 5 μm or less), it is preferably 0.5 μm or less.

[0046] The ceramic green sheet slurry may contain other polyvinyl acetal resins other than the polyvinyl acetal resin of the present invention, as well as other resins such as acrylic resins and ethyl cellulose, within the range that does not impair the effects of the present invention. In such cases, the content of the polyvinyl acetal resin of the present invention relative to the total binder resins is preferably 50% by weight or more.

[0047] If necessary, a dispersant, an antioxidant, an ultraviolet absorber, a surfactant, a filler, etc. may be added appropriately to the above-mentioned slurry for the ceramic green sheet, and in some cases, a small amount of other resin such as an acrylic resin or a urethane resin may also be added.

[0048] The method for producing the slurry for the ceramic green sheet is not particularly limited, and examples thereof include a method in which the polyvinyl acetal resin of the present invention, an organic solvent, a ceramic powder, and various additives to be added as needed are mixed using various mixers such as a ball mill, a blender mill, and a three-roll mill.

[0049] The ceramic green sheet slurry is applied, followed by heating and drying to obtain a ceramic green sheet. A ceramic electronic component can be manufactured using the ceramic green sheet. For example, a ceramic electronic component can be manufactured by carrying out a step of applying an electrode layer paste to the surface of the ceramic green sheet, and a step of stacking the ceramic green sheets on which the electrode layers have been formed, thermocompression bonding the resulting laminate, and then degreasing and firing the resulting laminate.

[0050] The method for applying the slurry composition for a ceramic green sheet is not particularly limited, and examples thereof include methods using a roll coater, a die coater, a curtain coater, etc. As for other specific methods, conventionally known methods can be used.

[0051] The ceramic electronic component is not particularly limited, and examples thereof include a multilayer ceramic capacitor, a multilayer ceramic inductor, a capacitor, a piezoelectric actuator, a multilayer varistor, a multilayer thermistor, an EMI filter, an aluminum nitride multilayer substrate, an alumina multilayer substrate, etc. Such a multilayer ceramic capacitor also constitutes one aspect of the present invention.

[0052] The method for producing the ceramic electronic component includes a step of applying an electrode layer paste to the surface of the ceramic green sheet. The electrode layer paste can be obtained by dissolving, for example, a polyvinyl acetal resin, ethyl cellulose, or acrylic resin as a binder resin in an organic solvent and dispersing a conductive powder or the like. These resins may be used alone or in combination. An electrode layer paste containing a polyvinyl acetal resin is preferred because it exhibits excellent adhesion to the ceramic green sheet during the thermocompression bonding step.

[0053] In the method for producing a ceramic electronic component, the ceramic green sheets having electrode layers formed thereon are prepared as described above, and then ceramic green sheets having electrode layers formed thereon that are prepared in the same manner are stacked and thermocompression-bonded to obtain a laminate, which is then degreased and fired, thereby obtaining a multilayer ceramic electronic component that solves problems such as sheet attack and cracking. Note that the thermocompression-bonding step and the steps of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used.

[0054] According to the present invention, it is possible to obtain a ceramic green sheet having high mechanical strength and suitable surface roughness, and it is possible to provide a polyvinyl acetal resin, a slurry for a ceramic green sheet, a ceramic green sheet, and a multilayer ceramic capacitor that can produce a highly reliable multilayer ceramic capacitor.

[0055] 1 is an example of an IR absorption spectrum obtained by measuring the IR absorption spectrum of a polyvinyl acetal resin of the present invention.

[0056] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0057] Example 1 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.1 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. The solution was cooled at 1°C / min and then maintained at 17°C for 1 hour. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added thereto. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0058] (Preparation of Ceramic Green Sheets) 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 stirred to dissolve, thereby preparing a resin solution. Also, 3 parts by weight of 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 stirred to dissolve. Next, 100 parts by weight of barium titanate powder (manufactured by Sakai Chemical Industry Co., Ltd., BT01) was added, and the mixture was stirred for 180 minutes in a bead mill (manufactured by Imex, Ready Mill) to prepare an inorganic dispersion. 100 parts by weight of the resin solution was added to the obtained inorganic dispersion and stirred in a bead mill to obtain a slurry composition. During stirring, sampling was performed every 5 minutes. 0.1 parts by weight of the resulting slurry composition was added to 10 parts by weight of an ethanol / toluene mixed solvent (1:1 by weight ratio), and the mixture was stirred using an ultrasonic disperser (US-303, manufactured by SND Corporation) to prepare a dispersion evaluation solution. Particle size distribution was measured using a laser diffraction particle size distribution analyzer (LA-910, manufactured by HORIBA Corporation), and stirring was terminated when the D50 value of the particle size distribution reached 1.0 μm. The resulting slurry composition was applied to a release-treated PET film using a coater to a thickness of 20 μm after drying, and then heated and dried to prepare a ceramic green sheet.

[0059] Example 2 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.2 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 10°C for 1 hour. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0060] Example 3 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.2 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 10°C for 1 hour. The temperature was then raised again to 55°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was held for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0061] Example 4 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.2 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 17°C for 1 hour. The temperature was then raised again to 55°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0062] Example 5: 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.4 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 17°C for 3 hours. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0063] Example 6 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.1 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 10°C for 1 hour. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was held for 3 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0064] Example 7 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.5 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 17°C for 3 hours. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 135 g of n-butyl aldehyde were added. The mixture was maintained for 1 hour to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0065] Example 8: 300 g of polyvinyl alcohol resin (average polymerization degree 780, molar saponification degree 98.9%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 20°C for 3 hours. The temperature was then raised again to 58°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 220 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0066] Example 9: 300 g of polyvinyl alcohol resin (average polymerization degree 4500, molar saponification degree 99.0%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 3°C / min and then held at 20°C for 1 hour. The temperature was then raised again to 50°C at 1.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was held for 3 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0067] Example 10: 300 g of polyvinyl alcohol resin (average polymerization degree 4500, molar saponification degree 99.2%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 20°C for 1 hour. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid, 120 g of n-butyl aldehyde, and 60 g of acetaldehyde were added. The mixture was then held for 3 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was prepared in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0068] Comparative Example 1 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.1 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 50°C without being cooled below the reaction temperature. Next, 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added to the solution, and the mixture was held for 6 hours to carry out an acetalization reaction [reaction step]. Subsequently, the mixture was neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0069] Comparative Example 2: 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.4 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 23°C for 1 hour. The temperature was then raised again to 55°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0070] Comparative Example 3: 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.0 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 17°C for 1 hour. The temperature was then raised again to 40°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was held for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0071] Comparative Example 4: 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.2 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 5°C for 1 hour. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added. The mixture was held for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0072] Comparative Example 5: 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 99.1 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then held at 10°C for 1 hour. The temperature was then raised again to 65°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 180 g of n-butyl aldehyde were added and held for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the obtained polyvinyl acetal resin was used.

[0073] Comparative Example 6: 300 g of polyvinyl alcohol resin (average polymerization degree 780, molar saponification degree 99.2%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 15°C for 3 hours. The temperature was then raised again to 47°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 100 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. Ceramic green sheets were produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0074] Comparative Example 7: 300 g of polyvinyl alcohol resin (average polymerization degree 1400, molar saponification degree 99.2%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 0.1°C / min and then maintained at 5°C for 3 hours. The temperature was then raised again to 55°C at 2°C / min, and 220 g of 35 wt% hydrochloric acid and 240 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. Ceramic green sheets were produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0075] Comparative Example 8: 300 g of polyvinyl alcohol resin (average degree of polymerization: 1200, degree of saponification: 24.7 mol%) was added to 300 g of pure water and dissolved by stirring at 90°C for approximately 2 hours. The solution was cooled at 1°C / min and then maintained at 10°C for 6 hours. The temperature was then raised again to 50°C at 0.5°C / min, and 220 g of 35 wt% hydrochloric acid and 160 g of n-butyl aldehyde were added. The mixture was maintained for 6 hours to carry out an acetalization reaction [reaction step]. The mixture was then neutralized, washed, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin. A ceramic green sheet was produced in the same manner as in Example 1, except that the resulting polyvinyl acetal resin was used.

[0076] (Evaluation) The polyvinyl acetal resins and ceramic green sheets obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.

[0077] (1) Evaluation of Polyvinyl Acetal Resin (1-1) Amount of Acetal Group, Amount of Hydroxyl Group, and Amount of Acetyl Group The polyvinyl acetal resin obtained was analyzed using an AV400 spectrometer (manufactured by Bruker). １ H-NMR measurement was carried out to calculate the amount of acetal groups, hydroxyl groups, and acetyl groups. ６ The solution was dissolved in water to a concentration of 1.6% by weight to prepare a measurement solution. １ H-NMR measurements were carried out at 80°C.

[0078] (1-2) Measurement of z-average molecular weight (THFMz, NMPMz) The obtained polyvinyl acetal resin was dissolved in tetrahydrofuran (THF) at a concentration of 0.2 wt%, passed through a PTFE filter with a pore size of 0.45 μm, and measured using a GPC apparatus HLC-8220 (manufactured by Tosoh Corporation) with THF as the mobile phase and a Bryce-type double-pass differential refractive index detector (manufactured by Tosoh Corporation) as the detector, at a flow rate of 0.35 mL / min using a TSKgel Super HZM-H (manufactured by Tosoh Corporation) column. The obtained measurement results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples to obtain the z-average molecular weight THFMz. Similarly, the obtained polyvinyl acetal resin was dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.2 wt %, passed through a PTFE filter with a pore size of 0.45 μm, and measured using a GPC apparatus GPC-101 (Shodex Corporation), NMP as the mobile phase, a differential refractive index detector RI-715 (Shodex Corporation) as the detector, and an LF-804 (Shodex Corporation) as the column, at a flow rate of 0.5 mL / min. The obtained measurement results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples to obtain the z-average molecular weight NMPMz. From the obtained THFMz and NMPMz, "THFMz-NMPMz" was calculated.

[0079] (1-3) IR absorption spectrum The obtained polyvinyl acetal resin was dissolved in a mixed solution of ethanol and toluene in a weight ratio of 1:1, and then coated on a PET film. －１ The film thickness of the measurement sample was adjusted so that the minimum transmittance of the peak appearing around 1000 nm was 20%, and a polyvinyl acetal resin sheet was obtained. The IR absorption spectrum of the obtained polyvinyl acetal resin sheet was measured using an infrared spectrophotometer (FT-720, manufactured by HORIBA) at 20°C. The measurement results showed that the IR absorption spectrum was measured at wavenumbers of 3050 to 3750 cm. －１A baseline was drawn for the peaks that appeared within this range, and peak analysis was performed on data that had been corrected so that the transmittances at both ends of the peak were 100%, and the minimum transmittance X, the transmittance a that satisfied [100-(100-X) / 2], and the wavenumbers A and B that indicated the transmittance a (%) (A was the wavenumber on the low wavenumber side, and B was the wavenumber on the high wavenumber side) were measured. １ The hydroxyl group amount calculated by H-NMR measurement was used to calculate the hydroxyl group amount converted wavenumber width (cm －１ / mol%)=[(B−A) / amount of hydroxyl groups] was calculated. １ The acetal group amount determined by H-NMR measurement was used to calculate the hydroxyl group-acetal group amount converted wavenumber width (cm －１ / mol%) = [(B - A) / amount of hydroxyl groups / amount of acetal groups]. Table 1 also shows the value of wave number A.

[0080] (1-4) Viscosity Measurement The obtained polyvinyl acetal resin was dissolved in a 1:1 weight ratio ethanol / toluene mixed solution to a concentration of 5% by mass to prepare a sample for viscosity measurement. The viscosity of the obtained sample for viscosity measurement was measured using a Brookfield viscometer at a solution temperature of 20°C. The Brookfield viscometer used was a TVB-10 viscometer (manufactured by Toki Sangyo Co., Ltd.), and the rotation speed and rotor were as follows: Examples 1 to 10, Comparative Examples 1 to 8: rotation speed 30 rpm, SPINDLE No. M1

[0081] (2) Evaluation of Ceramic Green Sheets (2-1) Tensile Modulus The tensile modulus (MPa) of the obtained ceramic green sheets was measured in accordance with JIS K 7113 using a tensile tester (AUTOGRAPH AGS-J, manufactured by Shimadzu Corporation) at a tension speed of 20 mm / min, and evaluated according to the following criteria: A: Tensile modulus of 1150 MPa or more B: Tensile modulus of 1090 MPa or more but less than 1150 MPa C: Tensile modulus of less than 1090 MPa

[0082] (2-2) Surface Roughness The ten-point average roughness (Rz) of the obtained ceramic green sheets was measured in accordance with JIS B 0601 (1994) and evaluated according to the following criteria: A: Rz is 0.27 μm or less B: Rz is more than 0.27 μm and 0.37 μm or less C: Rz is more than 0.37 μm

[0083]

[0084] According to the present invention, it is possible to obtain a ceramic green sheet having high mechanical strength and suitable surface roughness, and it is possible to provide a polyvinyl acetal resin, a slurry for a ceramic green sheet, a ceramic green sheet, and a multilayer ceramic capacitor that can produce a highly reliable multilayer ceramic capacitor.

Claims

1. In GPC measurement using a differential refractive index detector, the z-average molecular weight (THFMz) obtained using THF as the mobile phase and the z-average molecular weight (NMPMz) obtained using NMP as the mobile phase satisfy the following formula (1), and in the IR absorption spectrum measured by an infrared spectrophotometer, the wavenumber is 3050 to 3750 cm －１ When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B, １ A polyvinyl acetal resin having a hydroxyl group amount equivalent wavenumber width of 8.3 to 9.4, calculated by the following formula (2) using the amount of hydroxyl groups measured by H-NMR. －１ / mol%) = [(B - A) / amount of hydroxyl groups] (2) 2. The above A is 3220 cm －１ Above, 3415cm －１ 2. The polyvinyl acetal resin according to claim 1, wherein:

3. The above A, B and １ The polyvinyl acetal resin according to claim 1 or 2, wherein the hydroxyl group-acetal group amount-equivalent wavenumber width calculated by the following formula (3) using the hydroxyl group amount and acetal group amount measured by H-NMR is 0.120 to 0.135: －１ / mol% / mol%) = [(B - A) / amount of hydroxyl groups / amount of acetal groups] (3) 4. The polyvinyl acetal resin according to any one of claims 1 to 3, wherein a 5% by weight solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 64 mPa·s or more and 2,000 mPa·s or less when measured using a Brookfield viscometer at a solution temperature of 20°C.

5. The polyvinyl acetal resin according to any one of claims 1 to 4, wherein the amount of hydroxyl groups is 18 mol % or more and 40 mol % or less.

6. The polyvinyl acetal resin according to any one of claims 1 to 5, wherein the amount of acetyl groups is 0.1 mol % or more and 20 mol % or less.

7. A slurry for ceramic green sheets, comprising the polyvinyl acetal resin according to any one of claims 1 to 6, an organic solvent, and ceramic powder.

8. A ceramic green sheet obtained by using the slurry for ceramic green sheet according to claim 7.

9. A multilayer ceramic capacitor obtained by using the ceramic green sheet according to claim 8.

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