JP5625364B2 - Method for producing hexagonal ferrite particle powder, hexagonal ferrite particle powder, and magnetic recording medium - Google Patents
Method for producing hexagonal ferrite particle powder, hexagonal ferrite particle powder, and magnetic recording medium Download PDFInfo
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- JP5625364B2 JP5625364B2 JP2010011338A JP2010011338A JP5625364B2 JP 5625364 B2 JP5625364 B2 JP 5625364B2 JP 2010011338 A JP2010011338 A JP 2010011338A JP 2010011338 A JP2010011338 A JP 2010011338A JP 5625364 B2 JP5625364 B2 JP 5625364B2
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- Prior art keywords
- hexagonal ferrite
- particle powder
- ferrite particle
- magnetic recording
- magnetic
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- 239000002245 particle Substances 0.000 title claims description 135
- 229910000859 α-Fe Inorganic materials 0.000 title claims description 105
- 239000000843 powder Substances 0.000 title claims description 91
- 238000004519 manufacturing process Methods 0.000 title claims description 27
- 229910052751 metal Inorganic materials 0.000 claims description 28
- 239000002243 precursor Substances 0.000 claims description 27
- 239000002184 metal Substances 0.000 claims description 20
- 150000003839 salts Chemical class 0.000 claims description 19
- 239000000725 suspension Substances 0.000 claims description 16
- 238000010304 firing Methods 0.000 claims description 14
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 239000000243 solution Substances 0.000 claims description 13
- 230000004907 flux Effects 0.000 claims description 12
- 229910052788 barium Inorganic materials 0.000 claims description 7
- 229910052791 calcium Inorganic materials 0.000 claims description 7
- 239000011575 calcium Substances 0.000 claims description 7
- 229910052712 strontium Inorganic materials 0.000 claims description 7
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 6
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 150000002506 iron compounds Chemical class 0.000 claims description 6
- 229910021645 metal ion Inorganic materials 0.000 claims description 6
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 6
- 239000012670 alkaline solution Substances 0.000 claims description 3
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 21
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 18
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 18
- 238000000034 method Methods 0.000 description 18
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- 238000001035 drying Methods 0.000 description 9
- -1 organic acid salts Chemical class 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
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- 239000003973 paint Substances 0.000 description 8
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 7
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- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 6
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- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 4
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- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 4
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- 229910052700 potassium Inorganic materials 0.000 description 4
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- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 4
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
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- 125000003118 aryl group Chemical group 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- 150000001805 chlorine compounds Chemical class 0.000 description 3
- 239000011362 coarse particle Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
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- 229910052598 goethite Inorganic materials 0.000 description 3
- 150000004820 halides Chemical class 0.000 description 3
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 3
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- 239000011780 sodium chloride Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- QMMJWQMCMRUYTG-UHFFFAOYSA-N 1,2,4,5-tetrachloro-3-(trifluoromethyl)benzene Chemical compound FC(F)(F)C1=C(Cl)C(Cl)=CC(Cl)=C1Cl QMMJWQMCMRUYTG-UHFFFAOYSA-N 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 2
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
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- 229910052779 Neodymium Inorganic materials 0.000 description 2
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- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 150000001649 bromium compounds Chemical class 0.000 description 2
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- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 2
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- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
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- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
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Description
本発明は、六方晶フェライト粒子粉末に関するものであり、詳しくは、工業的な生産性に優れた水熱合成法による平均板面径が２０．５ｎｍを超えて３０ｎｍ以下である六方晶フェライト粒子粉末に関するものである。 The present invention relates to hexagonal ferrite particle powder, and more specifically, hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and not more than 30 nm by a hydrothermal synthesis method excellent in industrial productivity. It is about.
磁気記録技術は、従来、オーディオ用、ビデオ用、コンピューター用等をはじめとしてさまざまな分野で幅広く用いられている。近年、機器の小型軽量化、記録の長時間化及び記録容量の増大等が求められており、記録媒体に対しては、記録密度のより一層の向上が望まれている。 Conventionally, magnetic recording technology has been widely used in various fields including audio, video, and computer. In recent years, there has been a demand for smaller and lighter devices, longer recording time, increased recording capacity, and the like, and further improvement in recording density is desired for recording media.
従来の磁気記録媒体に対してより高密度記録を行うためには、高いＣ／Ｎ比が必要であり、ノイズ（Ｎ）が低く、再生出力（Ｃ）が高いことが求められている。近年では、これまで用いられていた誘導型磁気ヘッドに替わり、磁気抵抗型ヘッド（ＭＲヘッド）や巨大磁気抵抗型ヘッド（ＧＭＲヘッド）等の高感度ヘッドが開発されており、これらは誘導型磁気ヘッドに比べて再生出力が得られやすいことから、高いＣ／Ｎ比を得るためには、出力を上げるよりもノイズを低減する方が重要となってきている。 In order to perform high-density recording on a conventional magnetic recording medium, a high C / N ratio is required, noise (N) is low, and reproduction output (C) is required to be high. In recent years, high-sensitivity heads such as magnetoresistive heads (MR heads) and giant magnetoresistive heads (GMR heads) have been developed in place of the inductive magnetic heads used so far. Since it is easy to obtain a reproduction output as compared with the head, in order to obtain a high C / N ratio, it is more important to reduce the noise than to increase the output.
磁気記録媒体のノイズは、粒子性ノイズと磁気記録媒体の表面性に起因して発生する表面性ノイズに大別される。粒子性ノイズの場合、粒子サイズの影響が大きく、微粒子であるほどノイズ低減に有利であることから、磁気記録媒体に用いる磁性粒子粉末の粒子サイズはできるだけ小さいことが必要となるが、磁性粒子粉末は微細化することによって粒子体積が小さくなるため、磁化の熱的安定性を表す磁気異方性エネルギーと熱エネルギーとの比（ＫｕＶ／ｋＴ）（Ｋｕ：磁気異方性定数、Ｖ：粒子体積、ｋ：ボルツマン定数、Ｔ：絶対温度）が小さくなり、熱揺らぎの影響を受けやすくなる。 The noise of the magnetic recording medium is roughly classified into particulate noise and surface noise generated due to the surface property of the magnetic recording medium. In the case of particulate noise, the influence of the particle size is large, and the finer the particle, the better the noise reduction. Therefore, the magnetic particle powder used in the magnetic recording medium needs to be as small as possible. Since the particle volume is reduced by miniaturization, the ratio of magnetic anisotropy energy and thermal energy (KuV / kT) representing the thermal stability of magnetization (Ku: magnetic anisotropy constant, V: particle volume) , K: Boltzmann constant, T: absolute temperature) becomes small, and is susceptible to thermal fluctuations.
一般に、微粒子、且つ、高保磁力値を有する磁性粒子粉末としては、鉄を主成分とする金属磁性粒子粉末及び六方晶フェライト粒子粉末等が知られており、六方晶フェライト粒子粉末は針状の金属磁性粒子粉末に比べ短波長領域で高い出力が得られるという特徴があり、再生にＭＲヘッドやＧＭＲヘッドを用いた高密度記録の磁気記録媒体用磁性粉末として非常に有望である。 Generally, as magnetic particles having fine particles and a high coercive force value, metal magnetic particle powders mainly composed of iron, hexagonal ferrite particle powders, and the like are known, and hexagonal ferrite particle powders are acicular metal. Compared with magnetic particle powder, it has a feature that a high output can be obtained in a short wavelength region, and is very promising as a magnetic powder for high-density recording magnetic recording media using an MR head or GMR head for reproduction.
水熱合成法による六方晶フェライト粒子粉末としては、所望のフェライト組成のアルカリ性懸濁液を１００℃以上で液相加熱し、洗浄・乾燥した後９００℃前後で熱処理し、粉砕して六方晶フェライト粒子粉末を得る方法（特許文献１）、所望のフェライト組成のアルカリ性懸濁液を５０〜１５０℃の温度範囲で液相加熱し、得られた共沈物を水洗・乾燥した後６８０〜９００℃で熱処理し、粉砕して六方晶フェライト粒子粉末を得る方法（特許文献２）、所望のフェライト組成のアルカリ性懸濁液を、１００℃を超える温度でオートクレーブを用いて加熱し、洗浄・乾燥して六方晶フェライト粒子粉末を得る方法（特許文献３）等が知られている。 As the hexagonal ferrite particles by hydrothermal synthesis, an alkaline suspension having a desired ferrite composition is heated in a liquid phase at 100 ° C. or higher, washed and dried, heat treated at about 900 ° C., and pulverized to obtain hexagonal ferrite particles. A method for obtaining particle powder (Patent Document 1), an alkaline suspension having a desired ferrite composition is heated in a liquid phase in a temperature range of 50 to 150 ° C., and the resulting coprecipitate is washed and dried, followed by 680 to 900 ° C. Heat treatment and pulverization to obtain hexagonal ferrite particle powder (Patent Document 2), an alkaline suspension having a desired ferrite composition is heated at a temperature exceeding 100 ° C. using an autoclave, washed and dried. A method of obtaining hexagonal ferrite particle powder (Patent Document 3) is known.
水熱合成法による平均板面径が２０．５ｎｍを超えて３０ｎｍ以下である微細な六方晶フェライト粒子粉末は未だ得られていない。 A fine hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and not more than 30 nm by a hydrothermal synthesis method has not yet been obtained.
即ち、前出特許文献１には、水熱合成法によって得られた板状複合フェライト微粒子粉末が記載されているが、六方晶フェライト粒子粉末を構成する金属塩からなる懸濁液をアルカリ水溶液に徐添加することは考慮されておらず、また、従来の水熱合成法では平均粒子径が３０ｎｍ以下で保磁力（Ｈｃ）が９５．５ｋＡ／ｍ以上の磁気特性を有する六方晶フェライト粒子粉末を得ることは困難であった。 That is, in the above-mentioned Patent Document 1, a plate-like composite ferrite fine particle powder obtained by a hydrothermal synthesis method is described. A suspension composed of a metal salt constituting the hexagonal ferrite particle powder is made into an alkaline aqueous solution. Slow addition is not considered, and in the conventional hydrothermal synthesis method, hexagonal ferrite particles having an average particle size of 30 nm or less and a coercive force (Hc) of 95.5 kA / m or more are obtained. It was difficult to get.
また、前出特許文献２には、共沈−焼成法または水熱合成法によって得られた六方晶フェライト粒子粉末が記載されているが、六方晶フェライト粒子粉末を構成する金属塩からなる懸濁液をアルカリ水溶液に徐添加することは考慮されておらず、そのため、実施例で得られている六方晶フェライト粒子粉末は平均粒子径が一番小さいもので５３ｎｍであり、高密度記録用磁気記録媒体に用いるには粒子サイズが大きすぎると共に、保磁力（Ｈｃ）が９５．５ｋＡ／ｍ以上のものは得られていない。 In addition, Patent Document 2 described above describes a hexagonal ferrite particle powder obtained by a coprecipitation-firing method or a hydrothermal synthesis method. However, the suspension is composed of a metal salt constituting the hexagonal ferrite particle powder. It is not considered that the solution is gradually added to the alkaline aqueous solution. Therefore, the hexagonal ferrite particle powder obtained in the examples has the smallest average particle size of 53 nm, and the magnetic recording for high-density recording. A particle size that is too large for use in a medium and a coercive force (Hc) of 95.5 kA / m or more has not been obtained.
また、前出特許文献３には、水熱合成法によって得られた板状複合フェライト微粒子粉末が記載されているが、六方晶フェライト粒子粉末を構成する金属塩からなる懸濁液をアルカリ水溶液に徐添加することは考慮されておらず、そのため、実施例で得られている六方晶フェライト粒子粉末は平均粒子径が一番小さいもので５０ｎｍであり、高密度記録用磁気記録媒体に用いるには粒子サイズが大きすぎると共に、保磁力（Ｈｃ）が９５．５ｋＡ／ｍ以上のものは得られていない。 In addition, in the above-mentioned Patent Document 3, a plate-like composite ferrite fine particle powder obtained by a hydrothermal synthesis method is described. A suspension made of a metal salt constituting the hexagonal ferrite particle powder is made into an alkaline aqueous solution. Slow addition is not taken into consideration, so the hexagonal ferrite particle powder obtained in the examples has the smallest average particle diameter of 50 nm, and is used for a magnetic recording medium for high-density recording. A particle having a particle size that is too large and a coercive force (Hc) of 95.5 kA / m or more has not been obtained.
そこで、本発明は、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下である六方晶フェライト粒子粉末を水熱合成法によって得ることを技術的課題とする。 Then, this invention makes it a technical subject to obtain the hexagonal ferrite particle powder whose average plate surface diameter exceeds 20.5 nm and is 30 nm or less by a hydrothermal synthesis method.
前記技術的課題は、次の通りの本発明によって達成できる。 The technical problem can be achieved by the present invention as follows.
即ち、本発明は、バリウム、ストロンチウム、及びカルシウムより選ばれた少なくとも１種の金属イオンを含む金属塩と鉄化合物、並びに、２価乃至５価の金属元素から選ばれる１種又は２種以上の金属塩を混合した懸濁液を、アルカリ水溶液に添加した後、オートクレーブを用いて１００〜３００℃の温度範囲で反応し、得られた六方晶フェライト粒子の前駆体を濾別・乾燥し、次いで、融剤の存在下で６００〜８００℃の温度で焼成した後、融剤を除去することによって得られる六方晶フェライト粒子粉末の製造法において、前記懸濁液をアルカリ水溶液に添加する際に、２０分以上かけて徐添加することを特徴とする平均板面径が２０．５を超えて３０ｎｍ以下である六方晶フェライト粒子粉末の製造法である（本発明１）。 That is, the present invention provides a metal salt and an iron compound containing at least one metal ion selected from barium, strontium, and calcium, and one or more selected from divalent to pentavalent metal elements. The suspension in which the metal salt is mixed is added to the alkaline aqueous solution, then reacted in the temperature range of 100 to 300 ° C. using an autoclave, and the resulting hexagonal ferrite particle precursor is filtered and dried, In the method for producing hexagonal ferrite particles obtained by removing the flux after firing at a temperature of 600 to 800 ° C. in the presence of the flux, when adding the suspension to the aqueous alkaline solution, This is a method for producing hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 and 30 nm or less, characterized by being gradually added over 20 minutes (Invention 1).
本発明に係る水熱合成法による六方晶フェライト粒子粉末の製造法は、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下の微細な六方晶フェライト粒子粉末を工業的に有利に提供できるので、高密度磁気記録媒体の磁性粒子粉末の製造法として好適である。 The method for producing hexagonal ferrite particle powder by the hydrothermal synthesis method according to the present invention can industrially advantageously provide fine hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and not more than 30 nm. It is suitable as a method for producing magnetic particle powder for high-density magnetic recording media.
本発明に係る製造法によって得られた六方晶フェライト粒子粉末は、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下であると共に、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の範囲にあることから分散性に優れているため、高密度磁気記録媒体の磁性粒子粉末として好適である。 The hexagonal ferrite particle powder obtained by the production method according to the present invention has an average plate surface diameter of more than 20.5 nm and 30 nm or less, and an average plate surface diameter (L) and a BET specific surface area value (SSA). Since it is in a specific range and is excellent in dispersibility, it is suitable as a magnetic particle powder for a high-density magnetic recording medium.
本発明の構成をより詳しく説明すれば、次の通りである。 The configuration of the present invention will be described in more detail as follows.
先ず、本発明に係る六方晶フェライト粒子粉末の製造法について述べる。 First, a method for producing hexagonal ferrite particle powder according to the present invention will be described.
本発明に係る六方晶フェライト粒子粉末は、バリウム、ストロンチウム、及びカルシウムより選ばれた少なくとも１種の金属イオンを含む金属塩と鉄化合物、並びに、２価乃至５価の金属元素から選ばれる１種又は２種以上の金属塩を混合した懸濁液を、アルカリ水溶液に添加した後、オートクレーブを用いて１００〜３００℃の温度範囲で水熱反応を行い、得られた六方晶フェライト粒子の前駆体を濾別・乾燥し、次いで、融剤の存在下で６００〜８００℃の温度で焼成した後、融剤を除去することによって得られる六方晶フェライト粒子粉末の製造法において、前記懸濁液をアルカリ水溶液に添加する際に、２０分以上かけて徐添加することによって得ることができる。 The hexagonal ferrite particle powder according to the present invention is a metal salt containing at least one metal ion selected from barium, strontium, and calcium, an iron compound, and one kind selected from divalent to pentavalent metal elements. Alternatively, a suspension obtained by mixing two or more metal salts is added to an alkaline aqueous solution, and then subjected to a hydrothermal reaction in a temperature range of 100 to 300 ° C. using an autoclave, and the obtained precursor of hexagonal ferrite particles. In the process for producing hexagonal ferrite particle powder obtained by removing the flux after filtering and drying, then firing at a temperature of 600 to 800 ° C. in the presence of the flux, When it is added to the alkaline aqueous solution, it can be obtained by gradually adding it over 20 minutes.
また、本発明に係る六方晶フェライト粒子粉末のより好ましい製造法としては、上記製造法に加え、オートクレーブを用いて１００〜３００℃の温度範囲で反応後のスラリーを、スラリーに含まれる六方晶フェライト粒子の前駆体の体積挙動粒子径（Ｄ５０）が３０μｍ以下となるまで分散処理したものを焼成に用いることである。 Further, as a more preferable production method of the hexagonal ferrite particle powder according to the present invention, in addition to the above production method, a slurry after reaction in a temperature range of 100 to 300 ° C. using an autoclave is used, and the hexagonal ferrite contained in the slurry. What is subjected to dispersion treatment until the volume behavior particle diameter (D 50 ) of the particle precursor is 30 μm or less is used for firing.
本発明における鉄化合物としては、塩化物、臭化物、沃化物等のハロゲン化物、硝酸塩、硫酸塩、炭酸塩、有機酸塩及び錯塩等の水溶性の鉄塩から選ばれる１種又は２種以上を用いることができる。水への溶解性及び経済性を考慮すれば、塩化第二鉄及び硝酸第二鉄が好ましい。 As the iron compound in the present invention, one or more selected from water-soluble iron salts such as halides such as chloride, bromide and iodide, nitrates, sulfates, carbonates, organic acid salts and complex salts are used. Can be used. Considering solubility in water and economy, ferric chloride and ferric nitrate are preferable.
本発明におけるバリウム、ストロンチウム、及びカルシウムより選ばれた少なくとも１種の金属イオンを含む金属塩としては、水溶性の塩化物、臭化物、沃化物等のハロゲン化物又は硝酸塩を用いることができる。水への溶解性及び経済性を考慮すれば、塩化物が好ましい。 As the metal salt containing at least one metal ion selected from barium, strontium and calcium in the present invention, water-soluble chlorides, bromides, iodides and other halides or nitrates can be used. In view of solubility in water and economy, chloride is preferred.
本発明における２価乃至５価の金属元素（置換元素）から選ばれる１種又は２種以上の金属塩としては、水溶性の塩化物、臭化物、沃化物等のハロゲン化物又は硝酸塩を用いることができる。２価乃至５価の金属元素としては、具体的にはＣｏ、Ｎｉ、Ｚｎ、Ｍｎ、Ｍｇ、Ｔｉ、Ｓｎ、Ｚｒ、Ｃｕ、Ｍｏ、Ｌａ、Ｃｅ、Ｖ、Ｓｉ、Ｓｃ、Ｓｂ、Ｙ、Ｒｈ、Ｐｄ、Ｎｄ、Ｎｂ、Ｂ、Ｐ、Ｇｅ、Ａｌ、Ｒｕ、Ｐｒ、Ｂｉ、Ｗ、Ｒｅ等を用いることができる。 As one or more metal salts selected from divalent to pentavalent metal elements (substitution elements) in the present invention, water-soluble chlorides, bromides, iodides and other halides or nitrates may be used. it can. Specific examples of divalent to pentavalent metal elements include Co, Ni, Zn, Mn, Mg, Ti, Sn, Zr, Cu, Mo, La, Ce, V, Si, Sc, Sb, Y, and Rh. , Pd, Nd, Nb, B, P, Ge, Al, Ru, Pr, Bi, W, Re, or the like can be used.
本発明におけるアルカリ水溶液としては、水酸化ナトリウム、水酸化カリウム等の水酸化アルカリ水溶液を用いることができ、好ましくは、水酸化ナトリウムである。 As the aqueous alkali solution in the present invention, an aqueous alkali hydroxide solution such as sodium hydroxide or potassium hydroxide can be used, and sodium hydroxide is preferable.
アルカリ水溶液の濃度は、六方晶系フェライト粒子を構成する金属塩（鉄塩及び金属塩）の総量に対して、２．５〜１０倍であることが好ましく、より好ましくは４〜８倍である。アルカリ水溶液の濃度が高くなるに従って、得られる六方晶フェライト粒子粉末は微粒子化する傾向にあるが、１０倍程度でその効果は飽和するため、それ以上の添加は工業的に不利となる。 The concentration of the alkaline aqueous solution is preferably 2.5 to 10 times, more preferably 4 to 8 times the total amount of metal salts (iron salt and metal salt) constituting the hexagonal ferrite particles. . As the concentration of the aqueous alkali solution increases, the obtained hexagonal ferrite particle powder tends to become fine particles. However, since the effect is saturated at about 10 times, addition beyond that is industrially disadvantageous.
本発明において、前記バリウム、ストロンチウム、及びカルシウムより選ばれた少なくとも１種の金属イオンを含む金属塩と鉄化合物、並びに、２価乃至５価の金属元素から選ばれる１種又は２種以上の金属塩を混合した懸濁液を、前記アルカリ水溶液に添加する際に、２０分以上かけて徐添加することが重要であり、徐添加することで微細な六方晶フェライト粒子粉末を得ることが可能となる。懸濁液をアルカリ水溶液中に一度に添加した場合には、粗大粒子が生成しやすくなるため、微細な六方晶フェライト粒子粉末を得ることが困難となる。また、混在する粗大粒子に起因して粉体ＳＦＤが大きくなるため、良好な磁気特性を得ることが困難となる。 In the present invention, one or more metals selected from metal salts and iron compounds containing at least one metal ion selected from barium, strontium, and calcium, and divalent to pentavalent metal elements. When adding the suspension mixed with the salt to the alkaline aqueous solution, it is important to gradually add over 20 minutes, and by adding gradually, it is possible to obtain fine hexagonal ferrite particle powder. Become. When the suspension is added to the alkaline aqueous solution at once, coarse particles are likely to be generated, and it becomes difficult to obtain fine hexagonal ferrite particle powder. Further, since the powder SFD becomes large due to the mixed coarse particles, it is difficult to obtain good magnetic properties.
懸濁液をアルカリ水溶液に２０分以上かけて徐添加した後、オートクレーブを用いて１００〜３００℃の温度範囲で反応し、六方晶フェライト粒子の前駆体を含むスラリーを得る。反応温度は１１０〜２８０℃が好ましく、より好ましくは１２０〜２５０℃である。また、反応時間は３０分〜２４時間が好ましく、より好ましくは１時間〜２０時間である。 The suspension is gradually added to the aqueous alkali solution over 20 minutes and then reacted in the temperature range of 100 to 300 ° C. using an autoclave to obtain a slurry containing a precursor of hexagonal ferrite particles. The reaction temperature is preferably 110 to 280 ° C, more preferably 120 to 250 ° C. The reaction time is preferably 30 minutes to 24 hours, more preferably 1 hour to 20 hours.
得られた六方晶フェライト粒子の前駆体を含むスラリーは、反応により生成した塩及び未反応のアルカリを常法に従って水洗し、塩酸、硝酸及び酢酸等の酸を用いてｐＨ値を１０未満に調整する。 The obtained slurry containing the precursor of hexagonal ferrite particles was washed with water in accordance with a conventional method, the salt produced by the reaction and the unreacted alkali, and the pH value was adjusted to less than 10 using acids such as hydrochloric acid, nitric acid and acetic acid. To do.
なお、焼成に用いる六方晶フェライト粒子の前駆体は、六方晶フェライト粒子の前駆体を含むスラリー中の六方晶フェライト粒子の前駆体の体積挙動粒子径（Ｄ５０）が３０μｍ以下となるまであらかじめ分散させておくことが好ましく、より好ましくは２０μｍ以下である。分散処理は、ｐＨ値を調整する前後のどちらでもよいが、ｐＨ値調整後がより好ましい。六方晶フェライト粒子の前駆体を含むスラリーの分散方法としては、例えばビーズミル等を用いることができる。スラリー中の六方晶フェライト粒子の前駆体の体積挙動粒子径（Ｄ５０）を３０μｍ以下とし、あらかじめ粒子同士の凝集をほぐしておくことにより、その後の焼成工程においても粒子間の焼結が抑制されるため、微細な六方晶フェライト粒子粉末を得ることができる。 The precursor of hexagonal ferrite particles used for firing is dispersed in advance until the volume behavior particle size (D 50 ) of the precursor of hexagonal ferrite particles in the slurry containing the precursor of hexagonal ferrite particles is 30 μm or less. It is preferable to keep it, more preferably 20 μm or less. The dispersion treatment may be performed either before or after adjusting the pH value, but more preferably after adjusting the pH value. As a dispersion method of the slurry containing the precursor of hexagonal ferrite particles, for example, a bead mill can be used. By setting the volume behavior particle diameter (D 50 ) of the precursor of hexagonal ferrite particles in the slurry to 30 μm or less and loosening the aggregation of the particles in advance, sintering between the particles is suppressed even in the subsequent firing step. Therefore, fine hexagonal ferrite particle powder can be obtained.
次いで、ｐＨ値が調整された六方晶フェライト粒子の前駆体を含むスラリーに融剤を添加して攪拌・混合した後、融剤を添加した六方晶フェライト粒子の前駆体を含むスラリーの乾燥・粉砕を常法に従って行う。融剤としては、塩化ナトリウム及び塩化バリウム等の塩化物を用いることが好ましく、好ましくは塩化ナトリウムである。また、乾燥温度は１００〜２００℃が好ましく、より好ましくは１２０〜１８０℃である。 Next, after adding a flux to the slurry containing the hexagonal ferrite particle precursor whose pH value has been adjusted, stirring and mixing, drying and grinding the slurry containing the hexagonal ferrite particle precursor with the flux added In accordance with conventional methods. As the flux, it is preferable to use chlorides such as sodium chloride and barium chloride, preferably sodium chloride. Moreover, 100-200 degreeC is preferable for drying temperature, More preferably, it is 120-180 degreeC.
得られた六方晶フェライト粒子の前駆体の焼成は、６００〜８００℃の温度範囲で行う。焼成温度が６００℃未満の場合には、良好な磁気特性を有する六方晶フェライト粒子粉末を得ることが困難となる。焼成温度が８００℃を超える場合には、粒子が粗大化する傾向にあるため好ましくない。好ましい焼成温度は６５０〜７５０℃である。また、焼成時間は３０分〜６時間が好ましく、より好ましくは１時間〜５時間である。 Firing of the precursor of the obtained hexagonal ferrite particles is performed in a temperature range of 600 to 800 ° C. When the firing temperature is less than 600 ° C., it is difficult to obtain hexagonal ferrite particle powder having good magnetic properties. When the firing temperature exceeds 800 ° C., the particles tend to be coarse, which is not preferable. A preferable firing temperature is 650 to 750 ° C. The firing time is preferably 30 minutes to 6 hours, more preferably 1 hour to 5 hours.
得られた結晶化物は、湿式粉砕により粉砕後、該粉砕された結晶化物を含むスラリーを、塩酸、酢酸及び硝酸等の酸を用いて酸洗する。湿式粉砕には、ボール型混練機、ブレード型混練機、ホイール型混練機、ロール型混練機を用いることができ、振動ミル、回転ミル、サンドグラインダ等のボール型混練機及びラインミル、ヘンシェルミキサー、プラネタリーミキサー、ナウターミキサー等のブレード型混練機がより効果的に使用できる。 The obtained crystallized product is pulverized by wet pulverization, and the slurry containing the pulverized crystallized product is pickled using an acid such as hydrochloric acid, acetic acid, and nitric acid. For wet pulverization, ball type kneaders, blade type kneaders, wheel type kneaders, roll type kneaders can be used, ball type kneaders such as vibration mills, rotary mills, sand grinders and line mills, Henschel mixers, Blade type kneaders such as planetary mixers and nauter mixers can be used more effectively.
酸洗後のスラリーに水酸化ナトリウム等のアルカリ水溶液を添加してｐＨを５に調整した後、常法に従って水洗・乾燥・粉砕を行い、本発明に係る六方晶フェライト粒子粉末を得る。 An aqueous alkali solution such as sodium hydroxide is added to the acid-washed slurry to adjust the pH to 5, followed by washing, drying and pulverization according to a conventional method to obtain hexagonal ferrite particle powder according to the present invention.
本発明に係る六方晶フェライト粒子粉末は、六方晶フェライト粒子粉末の表面がアルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれた１種又は２種以上の化合物（以下、「アルミニウムの水酸化物等」という。）によって被覆されていることが好ましい。 The hexagonal ferrite particle powder according to the present invention is one or more selected from the group consisting of an aluminum hydroxide, an aluminum oxide, a silicon hydroxide and a silicon oxide. (Hereinafter referred to as “aluminum hydroxide or the like”).
アルミニウムの水酸化物等により被覆された六方晶フェライト粒子粉末は、六方晶フェライト粒子粉末を分散して得られる水懸濁液に、アルミニウム化合物、ケイ素化合物又は当該両化合物を添加して混合攪拌することにより、又は、必要により、混合攪拌後にｐＨ値を調整することにより、前記六方晶フェライト粒子粉末の粒子表面を、アルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれる一種又は二種以上の表面被覆物で被覆し、次いで、濾別、水洗、乾燥、粉砕することにより得ることができる。 The hexagonal ferrite particle powder coated with an aluminum hydroxide is added to an aqueous suspension obtained by dispersing the hexagonal ferrite particle powder, and the aluminum compound, the silicon compound or both of the compounds are mixed and stirred. Or, if necessary, by adjusting the pH value after mixing and stirring, the particle surface of the hexagonal ferrite particle powder is oxidized with aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon. It can be obtained by coating with one or two or more kinds of surface coatings selected from products, and then filtering, washing, drying and pulverizing.
アルミニウム化合物としては、酢酸アルミニウム、硫酸アルミニウム、塩化アルミニウム、硝酸アルミニウム等のアルミニウム塩や、アルミン酸ナトリウム等のアルミン酸アルカリ塩等が使用できる。 As the aluminum compound, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride, and aluminum nitrate, and alkali aluminates such as sodium aluminate can be used.
ケイ素化合物としては、３号水ガラス、オルトケイ酸ナトリウム、メタケイ酸ナトリウム等が使用できる。 As the silicon compound, No. 3 water glass, sodium orthosilicate, sodium metasilicate and the like can be used.
次いで、本発明に係る六方晶フェライト粒子粉末について述べる。 Next, the hexagonal ferrite particle powder according to the present invention will be described.
本発明に係る磁気記録媒体用六方晶フェライト粒子粉末は、前述の水熱合成法によって得られたものであり、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下であることを特徴とする。 The hexagonal ferrite particle powder for magnetic recording media according to the present invention is obtained by the hydrothermal synthesis method described above, and has an average plate surface diameter of more than 20.5 nm and 30 nm or less.
本発明に係る六方晶フェライト粒子粉末は、Ｂａ、Ｓｒ及びＣａから選ばれる１種又は２種以上の元素を含有するマグネトプランバイト型（Ｍ型）フェライト微粒子粉末又はＷ型フェライト微粒子粉末、あるいはそれらの原子の一部が他の元素で置換された六方晶フェライト粒子粉末である。置換元素としては、具体的にはＣｏ、Ｎｉ、Ｚｎ、Ｍｎ、Ｍｇ、Ｔｉ、Ｓｎ、Ｚｒ、Ｃｕ、Ｍｏ、Ｌａ、Ｃｅ、Ｖ、Ｓｉ、Ｓｃ、Ｓｂ、Ｙ、Ｒｈ、Ｐｄ、Ｎｄ、Ｎｂ、Ｂ、Ｐ、Ｇｅ、Ａｌ、Ｒｕ、Ｐｒ、Ｂｉ、Ｗ、Ｒｅ、等の元素を１種又は２種以上を用いることができる。 The hexagonal ferrite particle powder according to the present invention is a magnetoplumbite type (M type) ferrite fine particle powder or W type ferrite fine particle powder containing one or more elements selected from Ba, Sr and Ca, or these This is hexagonal ferrite particle powder in which some of the atoms are substituted with other elements. Specific examples of substitution elements include Co, Ni, Zn, Mn, Mg, Ti, Sn, Zr, Cu, Mo, La, Ce, V, Si, Sc, Sb, Y, Rh, Pd, Nd, and Nb. , B, P, Ge, Al, Ru, Pr, Bi, W, Re, and the like can be used alone or in combination.
本発明に係る六方晶フェライト粒子粉末の平均板面径は２０．５ｎｍを超えて３０ｎｍ以下であり、好ましくは２０．５ｎｍを超えて２８ｎｍ、より好ましくは２０．５ｎｍを超えて２６ｎｍである。六方晶フェライト粒子粉末の平均板面径が３０ｎｍを超える場合には、粒子サイズが大きいため、粒子性ノイズを低減することが難しく、高いＣ／Ｎ比を有する磁気記録媒体を得ることが困難となる。また、平均板面径が２０．５ｎｍ以下である場合には、磁性粒子粉末の微細化に伴う熱揺らぎの影響が大きくなるため好ましくない。 The average plate surface diameter of the hexagonal ferrite particle powder according to the present invention is more than 20.5 nm and not more than 30 nm, preferably more than 20.5 nm and 28 nm, more preferably more than 20.5 nm and 26 nm. When the average plate surface diameter of the hexagonal ferrite particle powder exceeds 30 nm, the particle size is large, so that it is difficult to reduce particulate noise, and it is difficult to obtain a magnetic recording medium having a high C / N ratio. Become. Moreover, when the average plate surface diameter is 20.5 nm or less, the influence of thermal fluctuation accompanying the refinement of the magnetic particle powder becomes large, which is not preferable.
本発明に係る六方晶フェライト粒子粉末の板状比（平均板面径と平均厚みの比）（以下、「板状比」という。）は１．５〜１０．０が好ましく、より好ましくは１．７５〜８．０、更により好ましくは２．０〜６．０である。板状比が１０を超える場合には、粒子間のスタッキングが多くなり、磁性塗料の製造時におけるビヒクル中への分散性が低下すると共に、粘度が増加する場合があるため好ましくない。 The plate ratio of the hexagonal ferrite particles according to the present invention (the ratio of the average plate surface diameter to the average thickness) (hereinafter referred to as “plate ratio”) is preferably 1.5 to 10.0, more preferably 1. .75 to 8.0, and still more preferably 2.0 to 6.0. When the plate ratio exceeds 10, stacking between particles increases, dispersibility in the vehicle during production of the magnetic coating material decreases, and viscosity may increase, which is not preferable.
本発明に係る六方晶フェライト粒子粉末の平均板面径（Ｌ）（ｎｍ）とＢＥＴ比表面積値（ＳＳＡ）（ｍ２／ｇ）との関係は下記式（１）で表される。
−１．０×Ｌ（ｎｍ）＋１２０ ≧ ＳＳＡ（ｍ２／ｇ） ≧ −１．０×Ｌ（ｎｍ）＋９０ ・・・ （１）
The relationship between the average plate surface diameter (L) (nm) and the BET specific surface area value (SSA) (m 2 / g) of the hexagonal ferrite particle powder according to the present invention is represented by the following formula (1).
−1.0 × L (nm) + 120 ≧ SSA (m 2 /g)≧−1.0×L (nm) +90 (1)
平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）との関係が上記式（１）の範囲にある場合、これを用いて磁気記録媒体を作製する際、磁性塗料中における分散性が向上するため、表面性に優れた磁気記録媒体を得ることができる。平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）との関係が上記式（１）の上限値を超える場合には、粒子の微細化による分子間力の増大により凝集を起こしやすいため、磁性塗料の製造時におけるビヒクル中への分散性が低下する。 When the relationship between the average plate surface diameter (L) and the BET specific surface area value (SSA) is in the range of the above formula (1), the dispersibility in the magnetic coating material is improved when a magnetic recording medium is produced using this. Therefore, a magnetic recording medium having excellent surface properties can be obtained. When the relationship between the average plate surface diameter (L) and the BET specific surface area value (SSA) exceeds the upper limit value of the above formula (1), aggregation is likely to occur due to an increase in intermolecular force due to particle refinement. Dispersibility in the vehicle during production of the magnetic coating is reduced.
本発明に係る六方晶フェライト粒子粉末の磁気特性は、保磁力（Ｈｃ）が９５．５〜３９７．９ｋＡ／ｍが好ましく、より好ましくは１１９．４〜３１８．３ｋＡ／ｍであり、飽和磁化値が４０〜７０Ａｍ２／ｋｇが好ましく、より好ましくは４５〜７０Ａｍ２／ｋｇである。また、粉体ＳＦＤは１．５以下であることが好ましく、より好ましくは１．４以下である。 As for the magnetic properties of the hexagonal ferrite particles according to the present invention, the coercive force (Hc) is preferably 95.5 to 397.9 kA / m, more preferably 119.4 to 318.3 kA / m, and the saturation magnetization value. Is preferably 40 to 70 Am 2 / kg, more preferably 45 to 70 Am 2 / kg. The powder SFD is preferably 1.5 or less, more preferably 1.4 or less.
本発明に係る六方晶フェライト粒子粉末は、必要により、六方晶フェライト粒子粉末の粒子表面を、アルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれた１種又は２種以上の化合物（以下、「アルミニウムの水酸化物等」という。）で被覆しておいてもよい。アルミニウムの水酸化物等で被覆処理を行うことにより、磁性塗料中に分散させた場合に、結合剤樹脂とのなじみがよく、所望の分散度がより得られ易い。 In the hexagonal ferrite particle powder according to the present invention, the surface of the hexagonal ferrite particle powder is selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide, if necessary. You may coat | cover with the seed | species or 2 or more types of compounds (henceforth "the hydroxide of aluminum etc."). By carrying out a coating treatment with aluminum hydroxide or the like, when dispersed in a magnetic paint, it is well-familiar with the binder resin and a desired degree of dispersion is more easily obtained.
次に、本発明に係る磁気記録媒体について述べる。 Next, the magnetic recording medium according to the present invention will be described.
本発明に係る磁気記録媒体は、本発明に係る六方晶フェライト粒子粉末と結合剤樹脂とを含む磁気記録層が非磁性支持体上に形成されてなる。また、必要に応じて、非磁性支持体と磁気記録層との間に非磁性下地層を形成してもよく、更に、非磁性支持体の一方の面に形成される磁気記録層に対し、非磁性支持体の他方の面にバックコート層を形成させてもよい。殊に、コンピューター記録用のバックアップテープの場合には、巻き乱れの防止や走行耐久性向上の点から、非磁性下地層やバックコート層を設けることが好ましい。 The magnetic recording medium according to the present invention is formed by forming a magnetic recording layer containing the hexagonal ferrite particle powder according to the present invention and a binder resin on a nonmagnetic support. Further, if necessary, a nonmagnetic underlayer may be formed between the nonmagnetic support and the magnetic recording layer, and further, with respect to the magnetic recording layer formed on one surface of the nonmagnetic support, A back coat layer may be formed on the other surface of the nonmagnetic support. In particular, in the case of a backup tape for computer recording, it is preferable to provide a nonmagnetic underlayer or a backcoat layer from the viewpoint of preventing winding disturbance and improving running durability.
本発明における非磁性支持体としては、現在、磁気記録媒体に汎用されているポリエチレンテレフタレート、ポリエチレンナフタレート等のポリエステル類、ポリエチレン、ポリプロピレン等のポリオレフィン類、ポリカーボネート、ポリアミド、ポリアミドイミド、ポリイミド、芳香族ポリアミド、芳香族ポリイミド、芳香族ポリアミドイミド、ポリスルフォン、セルローストリアセテート、ポリベンゾオキサゾール等の合成樹脂フィルム、アルミニウム、ステンレス等金属の箔や板及び各種の紙を使用することができる。 As the nonmagnetic support in the present invention, polyesters such as polyethylene terephthalate and polyethylene naphthalate that are currently widely used in magnetic recording media, polyolefins such as polyethylene and polypropylene, polycarbonate, polyamide, polyamideimide, polyimide, aromatic Synthetic resin films such as polyamide, aromatic polyimide, aromatic polyamideimide, polysulfone, cellulose triacetate, and polybenzoxazole, metal foils and plates such as aluminum and stainless steel, and various papers can be used.
結合剤樹脂としては、磁気記録媒体の製造にあたって汎用されている熱可塑性樹脂、熱硬化性樹脂、電子線硬化型樹脂等を単独又は組み合わせて用いることができる。 As the binder resin, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, etc. that are widely used in the production of magnetic recording media can be used alone or in combination.
本発明の磁気記録媒体において、非磁性支持体と磁気記録層との間に非磁性下地層を形成する場合、非磁性下地層中には非磁性粒子粉末と結合剤が含まれている。 In the magnetic recording medium of the present invention, when a nonmagnetic underlayer is formed between the nonmagnetic support and the magnetic recording layer, the nonmagnetic underlayer contains nonmagnetic particle powder and a binder.
非磁性下地層に用いられる非磁性粒子粉末としては、アルミナ、ヘマタイト、ゲータイト、酸化チタン、シリカ、酸化クロム、酸化セリウム、酸化亜鉛、チッ化珪素、窒化ホウ素、炭化ケイ素、炭酸カルシウム及び硫酸バリウム等を、単独又は組合せて用いることができる。好ましくはヘマタイト、ゲータイト、酸化チタンであり、より好ましくはヘマタイトである。 Nonmagnetic particle powders used for the nonmagnetic underlayer include alumina, hematite, goethite, titanium oxide, silica, chromium oxide, cerium oxide, zinc oxide, silicon nitride, boron nitride, silicon carbide, calcium carbonate, and barium sulfate. Can be used alone or in combination. Hematite, goethite and titanium oxide are preferred, and hematite is more preferred.
前記非磁性粒子粉末の粒子形状は、針状、紡錘状、米粒状、球状、粒状、多面体状、フレーク状、鱗片状及び板状等のいずれの形状であってもよい。粒子サイズは、好ましくは０．００５〜０．３０μｍであり、より好ましくは０．０１０〜０．２５μｍである。また、必要により、粒子表面をアルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれた１種又は２種以上の化合物で被覆してもよく、化合物で被覆しない場合に比べ、非磁性塗料中での分散性を改善することができる。 The particle shape of the non-magnetic particle powder may be any shape such as needle shape, spindle shape, rice grain shape, spherical shape, granular shape, polyhedron shape, flake shape, scale shape and plate shape. The particle size is preferably 0.005 to 0.30 μm, more preferably 0.010 to 0.25 μm. If necessary, the particle surface may be coated with one or more compounds selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. Compared with the case of not coating, dispersibility in the nonmagnetic paint can be improved.
結合剤樹脂としては、前記磁気記録層を作製するために用いた結合剤樹脂を使用することができる。 As the binder resin, the binder resin used for producing the magnetic recording layer can be used.
本発明の磁気記録媒体において、非磁性支持体の一方の面に形成される磁気記録層に対し、非磁性支持体の他方の面にバックコート層を形成する場合、バックコート層中には、結合剤樹脂と共に、バックコート層の表面電気抵抗値及び強度向上を目的として、帯電防止剤及び無機粒子粉末を含有させることが好ましい。 In the magnetic recording medium of the present invention, when a backcoat layer is formed on the other surface of the nonmagnetic support relative to the magnetic recording layer formed on one surface of the nonmagnetic support, It is preferable to contain an antistatic agent and inorganic particle powder together with the binder resin for the purpose of improving the surface electrical resistance value and strength of the backcoat layer.
無機粉末としては、アルミナ、ヘマタイト、ゲータイト、酸化チタン、シリカ、酸化クロム、酸化セリウム、酸化亜鉛、チッ化珪素、窒化ホウ素、炭化ケイ素、炭酸カルシウム及び硫酸バリウム等から選ばれる１種又は２種以上を用いることができる。粒子サイズは、好ましくは０．００５〜１．０μｍであり、より好ましくは０．０１０〜０．５μｍである。 As the inorganic powder, one or more selected from alumina, hematite, goethite, titanium oxide, silica, chromium oxide, cerium oxide, zinc oxide, silicon nitride, boron nitride, silicon carbide, calcium carbonate, barium sulfate, etc. Can be used. The particle size is preferably 0.005 to 1.0 [mu] m, more preferably 0.010 to 0.5 [mu] m.
帯電防止剤としては、カーボンブラック、グラファイト、酸化スズ、酸化チタン−酸化スズ−酸化アンチモン等の導電性粉末及び界面活性剤等を用いることができる。帯電防止の他に、摩擦係数低減、磁気記録媒体の強度向上といった効果が期待できることから、帯電防止剤としては、カーボンブラックを用いることが好ましい。 As the antistatic agent, conductive powder such as carbon black, graphite, tin oxide, titanium oxide-tin oxide-antimony oxide, a surfactant, and the like can be used. In addition to antistatic properties, carbon black is preferably used as the antistatic agent since effects such as reduction of the friction coefficient and improvement of the strength of the magnetic recording medium can be expected.
結合剤樹脂としては、前記磁気記録層、及び非磁性下地層を作製するために用いた結合剤樹脂を使用することができる。 As the binder resin, the binder resin used for producing the magnetic recording layer and the nonmagnetic underlayer can be used.
本発明における磁気記録層、非磁性下地層及びバックコート層中には、必要に応じて、磁気記録媒体の製造に通常用いられている潤滑剤、研磨剤、分散剤、帯電防止剤等を添加してもよい。 In the magnetic recording layer, nonmagnetic underlayer and backcoat layer in the present invention, lubricants, abrasives, dispersants, antistatic agents, etc., which are usually used in the production of magnetic recording media are added as necessary. May be.
本発明に係る磁気記録媒体は、保磁力（Ｈｃ）が９５．５〜３５８．１ｋＡ／ｍ、好ましくは５１．７〜３１８．３ｋＡ／ｍ、保磁力分布ＳＦＤ（Ｓｗｉｔｃｈｉｎｇ Ｆｉｅｌｄ Ｄｉｓｔｒｉｂｕｔｉｏｎ）が、０．７０以下、好ましくは０．６７以下、より好ましくは０．６５以下である。 The magnetic recording medium according to the present invention has a coercive force (Hc) of 95.5 to 358.1 kA / m, preferably 51.7 to 318.3 kA / m, and a coercive force distribution SFD (Switching Field Distribution) of 0. 70 or less, preferably 0.67 or less, more preferably 0.65 or less.
次に、本発明における磁気記録媒体の製造法について述べる。 Next, a method for manufacturing a magnetic recording medium in the present invention will be described.
前記非磁性下地層、磁気記録層、及びバックコート層の形成にあたって用いる溶剤としては、磁気記録媒体に汎用されているアセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン及びテトラヒドロフラン等のケトン類、トルエン、キシレン等の芳香族炭化水素類、メタノール、エタノール、プロパノール、ブタノール、イソブチルアルコール及びイソプロピルアルコール等のアルコール類、酢酸メチル、酢酸ブチル、酢酸イソブチル及び酢酸グリコール等のエステル類、グリコールジメチルエーテル、グリコールモノエチルエーテル及びジオキサン等のグリコールエーテル類及びその混合物等を使用することができる。 Solvents used in forming the nonmagnetic underlayer, magnetic recording layer, and backcoat layer include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and tetrahydrofuran, toluene, xylene, and the like that are widely used in magnetic recording media. Aromatic hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol, isobutyl alcohol and isopropyl alcohol, esters such as methyl acetate, butyl acetate, isobutyl acetate and glycol acetate, glycol dimethyl ether, glycol monoethyl ether and dioxane Glycol ethers and mixtures thereof can be used.
非磁性下地層、磁気記録層、バックコート層は、各層を構成する成分及び溶剤を一般に使用される混練機及び分散機により混練・分散処理を行い、各塗料を作製する。該各塗料を用いて、非磁性支持体上の一面に非磁性下地層、磁気記録層の順に塗布、乾燥後、カレンダー処理を行う。その際の塗布方法としては、磁性層と非磁性層をほぼ同時に塗布するＷｅｔ ｏｎ Ｗｅｔ法でも、非磁性下地層を塗布・乾燥後、その上に磁気記録層を塗布するＷｅｔ ｏｎ Ｄｒｙ法のどちらでもよい。また、必要により、バックコート層を設ける場合には、非磁性下地層及び磁気記録層とは反対面の非磁性支持体上にバックコート層用塗料を塗布、乾燥後、カレンダー処理を行い、磁気記録媒体を得る。 The nonmagnetic underlayer, the magnetic recording layer, and the backcoat layer are kneaded and dispersed with a kneader and a disperser that generally use components and solvents that constitute each layer, thereby preparing each paint. Using each of the coating materials, a nonmagnetic underlayer and a magnetic recording layer are applied in this order on one surface of the nonmagnetic support, dried, and then calendared. As a coating method at that time, either the Wet on Wet method in which the magnetic layer and the nonmagnetic layer are applied almost simultaneously, or the Wet on Dry method in which the nonmagnetic underlayer is applied and dried and then the magnetic recording layer is applied thereon. But you can. If necessary, if a backcoat layer is provided, a backcoat layer coating is applied on the nonmagnetic support opposite to the nonmagnetic underlayer and the magnetic recording layer, dried, calendered, and magnetically treated. A recording medium is obtained.
＜作用＞
本発明において重要な点は、バリウム、ストロンチウム、及びカルシウムより選ばれた少なくとも１種の金属イオンを含む金属塩と鉄化合物、並びに、２価乃至５価の金属元素から選ばれる１種又は２種以上の金属塩を混合した懸濁液を、アルカリ水溶液に添加した後、オートクレーブを用いて１００〜３００℃の温度範囲で反応し、得られた六方晶フェライト粒子の前駆体を濾別・乾燥し、次いで、融剤の存在下で６００〜８００℃の温度で焼成した後、融剤を除去することによって得られる六方晶フェライト粒子粉末の製造法において、前記懸濁液をアルカリ水溶液に添加する際に、２０分以上かけて徐添加することにより、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下である六方晶フェライト粒子粉末を得ることができるという事実である。
<Action>
The important point in the present invention is that one or two metal salts and iron compounds containing at least one metal ion selected from barium, strontium and calcium, and one or two metal elements selected from divalent to pentavalent metal elements are used. The suspension obtained by mixing the above metal salts is added to an alkaline aqueous solution, then reacted in an autoclave at a temperature range of 100 to 300 ° C., and the obtained hexagonal ferrite particle precursor is filtered and dried. Then, in the method for producing hexagonal ferrite particle powder obtained by firing at a temperature of 600 to 800 ° C. in the presence of a flux and then removing the flux, the suspension is added to an aqueous alkaline solution. In addition, by gradually adding over 20 minutes, hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and 30 nm or less can be obtained. It is.
本発明に係る六方晶フェライト粒子粉末の製造法によって、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下である微細な六方晶フェライト粒子粉末を得ることができた理由として、本発明者は次のように考えている。懸濁液をアルカリ水溶液中に一度に添加した場合には粗大粒子が生成しやすくなるが、２０分以上かけて徐添加することにより、得られる六方晶フェライト粒子の前駆体は微細な粒子となり、これをプリカーサーとして用いることにより、微細な六方晶フェライト粒子粉末を得ることができたものと考えている。 As a reason why the fine hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and 30 nm or less can be obtained by the method for producing the hexagonal ferrite particle powder according to the present invention, the present inventor I think like that. When the suspension is added to the alkaline aqueous solution all at once, coarse particles are likely to be generated, but by gradually adding over 20 minutes, the obtained hexagonal ferrite particle precursor becomes fine particles, It is considered that fine hexagonal ferrite particle powder could be obtained by using this as a precursor.
以下に、本発明における実施例を示し、本発明を具体的に説明する。 Examples of the present invention are shown below, and the present invention will be specifically described.
六方晶フェライト粒子粉末及び磁気記録媒体用磁性微粒子粉末の平均板面径及び平均厚さは、透過型電子顕微鏡を用いて粒子の写真を撮影し、該写真を用いて粒子３６０個以上について板面径、厚さをそれぞれ測定し、その平均値で粒子の平均板面径及び平均厚さを示した。なお、粒子の選定基準としては、粒子同士が重なっており、境界がはっきりしていないものは測定を行わないものとした。 The average plate surface diameter and average thickness of the hexagonal ferrite particle powder and the magnetic fine particle powder for a magnetic recording medium are obtained by taking a photograph of the particles using a transmission electron microscope and using the photograph for the plate surface of 360 or more particles. The diameter and the thickness were measured, and the average value of the average plate surface diameter and the average thickness of the particles was shown. In addition, as a selection criterion for particles, particles that overlap each other and whose boundaries are not clear are not measured.
板状比は、平均板面径と平均厚さとの比で示した。 The plate ratio was shown as the ratio between the average plate surface diameter and the average thickness.
比表面積は、「モノソーブＭＳ−１１」（カンタクロム株式会社製）を用いて、ＢＥＴ法により測定した値で示した。 The specific surface area was shown by the value measured by BET method using “Monosorb MS-11” (manufactured by Kantachrome Co., Ltd.).
六方晶フェライト粒子粉末に含有される各種元素の含有量は、「蛍光Ｘ線分析装置３０６３Ｍ型」（理学電機工業株式会社製）を使用し、ＪＩＳ Ｋ０１１９の「けい光Ｘ線分析通則」に従って測定した。 The content of various elements contained in the hexagonal ferrite particle powder is measured using a “fluorescence X-ray analyzer 3063M type” (manufactured by Rigaku Denki Kogyo Co., Ltd.) according to “General X-ray fluorescence analysis rules” of JIS K0119. did.
スラリー中に含まれる六方晶フェライト粒子の前駆体の体積基準平均粒子径（Ｄ５０）は、「レーザー回折式粒度分布測定装置 ｍｏｄｅｌ ＨＥＬＯＳ ＬＡ／ＫＡ」（ＳＹＭＰＡＴＥＣ社製）の湿式分散ユニットを用いて測定した。 The volume-based average particle diameter (D 50 ) of the precursor of hexagonal ferrite particles contained in the slurry is determined using a wet dispersion unit of “Laser diffraction particle size distribution measuring device model HELOS LA / KA” (manufactured by SYMPATEC). It was measured.
六方晶フェライト粒子粉末及び磁気テープの磁気特性は、「振動試料型磁力計ＶＳＭ ＳＳＭ−５−１５」（東英工業株式会社製）を用いて外部磁場１１９３．７ｋＡ／ｍの条件で測定した。また、粉体ＳＦＤ及び磁気テープのＳＦＤは、印加磁場が０〜３９７．９ｋＡ／ｍの範囲ではスイープ速度を７９．６（ｋＡ／ｍ）／分とし、３９７．９〜１，１９３．７ｋＡ／ｍの範囲ではスイープ速度を３９７．９（ｋＡ／ｍ）／分として測定した。 The magnetic properties of the hexagonal ferrite particle powder and the magnetic tape were measured using a “vibrating sample magnetometer VSM SSM-5-15” (manufactured by Toei Kogyo Co., Ltd.) under an external magnetic field of 1193.7 kA / m. The powder SFD and the SFD of the magnetic tape have a sweep speed of 79.6 (kA / m) / min when the applied magnetic field is in the range of 0 to 397.9 kA / m, and is 397.9 to 1,193.7 kA / min. In the range of m, the sweep rate was measured as 397.9 (kA / m) / min.
磁気テープの塗膜表面の光沢度は、「グロスメーター ＵＧＶ−５Ｄ」（スガ試験機株式会社製）を用いて入射角４５°で測定した値であり、標準板光沢を８６．３％とした時の値を％で示したものである。 The glossiness of the coating film surface of the magnetic tape is a value measured at an incident angle of 45 ° using “Gloss meter UGV-5D” (manufactured by Suga Test Instruments Co., Ltd.), and the standard plate gloss is 86.3%. The hour value is shown in%.
表面粗度Ｒａは、「ＺＹＧＯ ＮｅｗＶｉｅｗ６００Ｓ」（ＺＹＧＯ株式会社製）を用いて塗膜の中心線平均粗さを測定した。 Surface roughness Ra measured the centerline average roughness of the coating film using "ZYGO NewView600S" (made by ZYGO Corporation).
磁気記録媒体を構成する非磁性支持体及び磁気記録層の各層の厚みは、デジタル電子マイクロメーターＫ３５１Ｃ（安立電気株式会社製）を用いて測定した。 The thickness of each layer of the nonmagnetic support and the magnetic recording layer constituting the magnetic recording medium was measured using a digital electronic micrometer K351C (manufactured by Anritsu Electric Co., Ltd.).
＜実施例１−１：磁気記録媒体用六方晶フェライト粒子粉末の製造＞
ＢａＣｌ２・２Ｈ２Ｏ ０．０８ｍｏｌ、ＦｅＣｌ３・６Ｈ２Ｏ ０．６０ｍｏｌ、ＮｉＣｌ２ ０．０１８ｍｏｌ、ＴｉＣｌ４ ０．０１８ｍｏｌに純水を加えて溶解し、０．７Ｌの混合溶液を調製した。次いで、１８．５５ｍｏｌ／ＬのＮａＯＨ水溶液０．５Ｌを攪拌させながら前記混合溶液を２０ｍＬ／ｍｉｎ．の流量で３５分間かけてＮａＯＨ水溶液中に添加した後、オートクレーブを用いて１５０℃で２４０分反応を行った。
<Example 1-1: Production of hexagonal ferrite particle powder for magnetic recording medium>
Pure water was added and dissolved in BaCl 2 .2H 2 O 0.08 mol, FeCl 3 .6H 2 O 0.60 mol, NiCl 2 0.018 mol, TiCl 4 0.018 mol to prepare a 0.7 L mixed solution. Next, while stirring 0.5 L of 18.55 mol / L NaOH aqueous solution, the mixed solution was added at 20 mL / min. Was added to an aqueous NaOH solution at a flow rate of 35 minutes, followed by reaction at 150 ° C. for 240 minutes using an autoclave.
次に、得られた六方晶フェライト粒子の前駆体のスラリーを、純水を用いて十分に水洗し、六方晶フェライト粒子の前駆体を含む１Ｌのスラリーとした後、塩酸を用いてｐＨ値を８．５に調整し、超音波ホモジナイザー（ＢＲＡＮＳＯＮ株式会社製ＳｏｎｉｆｉｅｒＩＩ ｍｏｄｅｌ ４５０Ｄ）を用いて１０分間攪拌し、分散処理を行った。なお、この時のスラリー中の六方晶フェライト粒子の前駆体の体積挙動粒子径（Ｄ５０）は１．６μｍであった。 Next, the obtained slurry of the hexagonal ferrite particle precursor is sufficiently washed with pure water to obtain a 1 L slurry containing the hexagonal ferrite particle precursor, and then the pH value is adjusted with hydrochloric acid. The mixture was adjusted to 8.5 and stirred for 10 minutes using an ultrasonic homogenizer (Sonifier II model 450D manufactured by BRANSON Co., Ltd.) for dispersion treatment. The volume behavior particle diameter (D 50 ) of the precursor of hexagonal ferrite particles in the slurry at this time was 1.6 μm.
次いで、前記六方晶フェライト粒子の前駆体を含むスラリーに、フラックスとしてＮａＣｌを六方晶フェライト粒子の前駆体１００重量部に対して３０重量部添加し、ろ過・乾燥を行って、六方晶フェライト粒子の前駆体を得た。なお、乾燥温度は１５０℃で行った。 Next, 30 parts by weight of NaCl as a flux with respect to 100 parts by weight of the hexagonal ferrite particle precursor is added to the slurry containing the hexagonal ferrite particle precursor, followed by filtration and drying. A precursor was obtained. The drying temperature was 150 ° C.
得られた乾燥した六方晶フェライト粒子の前駆体を、空気中７００℃の温度で１２０分焼成し、得られた焼成物に純水１Ｌを加えて分散スラリーとした。得られたスラリーを湿式粉砕した後、塩酸を用いてｐＨ値を２に調製して６０分保持することにより酸処理を行い、水酸化ナトリウム水溶液を用いてｐＨ値を５に調整した後、水洗・ろ過・乾燥・粉砕して、実施例１−１の六方晶フェライト粒子粉末を得た。 The obtained precursor of the dried hexagonal ferrite particles was fired in air at a temperature of 700 ° C. for 120 minutes, and 1 L of pure water was added to the fired product to obtain a dispersed slurry. The obtained slurry was wet pulverized, acid-treated by adjusting the pH value to 2 with hydrochloric acid and maintaining for 60 minutes, adjusted to pH value 5 with an aqueous sodium hydroxide solution, and then washed with water. -Filtration, drying, and pulverization gave the hexagonal ferrite particle powder of Example 1-1.
得られた六方晶フェライト粒子粉末は板状であり、平均板面径は２２．７ｎｍ、平均厚みは６．７ｎｍ、板状比は３．４、ＢＥＴ比表面積値（実測値）は７３．８ｍ２／ｇ、保磁力（Ｈｃ）は１８８．３ｋＡ／ｍ、飽和磁化（σｓ）は４８．０Ａｍ２／ｋｇ、粉体ＳＦＤは０．８４であった。 The obtained hexagonal ferrite particle powder has a plate shape, an average plate surface diameter of 22.7 nm, an average thickness of 6.7 nm, a plate ratio of 3.4, and a BET specific surface area value (measured value) of 73.8 m. The coercive force (Hc) was 188.3 kA / m, the saturation magnetization (σs) was 48.0 Am 2 / kg, and the powder SFD was 0.84.
＜実施例２−１：磁気記録媒体の製造＞
非磁性下地層形成用の非磁性塗料組成
非磁性下地層用ヘマタイト粒子粉末 １００．０重量部、
スルホン酸カリウム基を有する塩化ビニル系共重合樹脂 １１．８重量部、
スルホン酸ナトリウム基を有するポリウレタン樹脂 １１．８重量部、
シクロヘキサノン ７８．３重量部、
メチルエチルケトン １９５．８重量部、
トルエン １１７．５重量部、
硬化剤（ポリイソシアネート） ３．０重量部、
潤滑剤（ブチルステアレート） １．０重量部。
<Example 2-1: Production of magnetic recording medium>
Nonmagnetic coating composition for nonmagnetic underlayer formation 100.0 parts by weight of hematite particle powder for nonmagnetic underlayer,
11.8 parts by weight of a vinyl chloride copolymer resin having a potassium sulfonate group,
11.8 parts by weight of a polyurethane resin having a sodium sulfonate group,
78.3 parts by weight of cyclohexanone,
195.8 parts by weight of methyl ethyl ketone,
117.5 parts by weight of toluene,
Curing agent (polyisocyanate) 3.0 parts by weight,
Lubricant (butyl stearate) 1.0 part by weight.
非磁性下地層用ヘマタイト粒子粉末と結合剤樹脂溶液（スルホン酸カリウム基を有する塩化ビニル系共重合樹脂３０重量％とシクロヘキサノン７０重量％）及びシクロヘキサノンとを固形分が７２ｗｔ％となるよう混合し、自動乳鉢を用いて３０分間混練して混練物を得た。 A non-magnetic underlayer hematite particle powder, a binder resin solution (vinyl chloride copolymer resin having potassium sulfonate group 30 wt% and cyclohexanone 70 wt%) and cyclohexanone are mixed so that the solid content is 72 wt%; A kneaded product was obtained by kneading for 30 minutes using an automatic mortar.
次いで、上記非磁性塗料組成となるように、上記混練物と、追加の結合剤樹脂溶液（スルホン酸ナトリウム基を有するポリウレタン樹脂３０重量％、溶剤（メチルエチルケトン：トルエン＝１：１）７０重量％）、シクロヘキサノン、メチルエチルケトン及びトルエン１．５ｍｍφガラスビーズ９５ｇと共に１４０ｍｌのガラス瓶に添加し、ペイントシェーカーで６時間混合・分散を行って非磁性塗料組成物を得た。その後、潤滑剤及び硬化剤を加え、更に、ペイントシェーカーで１５分間混合・分散した後、３μｍの平均孔径を有するフィルターを用いてろ過し、非磁性下地層用非磁性塗料を調整した。 Next, the kneaded product and an additional binder resin solution (30% by weight of a polyurethane resin having a sodium sulfonate group, 70% by weight of a solvent (methyl ethyl ketone: toluene = 1: 1)) so that the nonmagnetic coating composition is obtained. The mixture was added to a 140 ml glass bottle together with 95 g of cyclohexanone, methyl ethyl ketone and toluene 1.5 mmφ glass beads, and mixed and dispersed in a paint shaker for 6 hours to obtain a nonmagnetic coating composition. Thereafter, a lubricant and a curing agent were added, and further mixed and dispersed for 15 minutes with a paint shaker, followed by filtration using a filter having an average pore diameter of 3 μm to prepare a nonmagnetic paint for a nonmagnetic underlayer.
上記非磁性下地層用非磁性塗料を厚さ４．５μｍの芳香族ポリアミドフィルム上に塗布し、次いで、乾燥させることにより非磁性下地層を形成した。 The nonmagnetic coating for the nonmagnetic underlayer was applied onto an aromatic polyamide film having a thickness of 4.5 μm, and then dried to form a nonmagnetic underlayer.
磁気記録層形成用の磁性塗料組成
六方晶フェライト粒子粉末 １００．０重量部、
スルホン酸カリウム基を有する塩化ビニル系共重合樹脂 １２．５重量部、
スルホン酸ナトリウム基を有するポリウレタン樹脂 ７．５重量部、
研磨剤（ＡＫＰ−５０） ５．０重量部、
カーボンブラック ２．０重量部、
潤滑剤（ミリスチン酸：ステアリン酸ブチル＝１：２） ３．０重量部、
硬化剤（ポリイソシアネート） ５．０重量部、
シクロヘキサノン １７０．０重量部、
メチルエチルケトン １７０．０重量部。
100.0 parts by weight of a magnetic coating composition hexagonal ferrite particle powder for forming a magnetic recording layer,
12.5 parts by weight of a vinyl chloride copolymer resin having a potassium sulfonate group,
7.5 parts by weight of a polyurethane resin having a sodium sulfonate group,
Abrasive (AKP-50) 5.0 parts by weight,
2.0 parts by weight of carbon black,
Lubricant (myristic acid: butyl stearate = 1: 2) 3.0 parts by weight,
Curing agent (polyisocyanate) 5.0 parts by weight,
170.0 parts by weight of cyclohexanone,
170.0 parts by weight of methyl ethyl ketone.
六方晶フェライト粒子粉末と研磨剤、カーボンブラック、結合剤樹脂溶液（スルホン酸カリウム基を有する塩化ビニル系共重合樹脂３０重量％とシクロヘキサノン７０重量％）及びシクロヘキサノンとを固形分が７６ｗｔ％となるよう混合し、自動乳鉢を用いて４０分間混練して混練物を得た。 Hexagonal ferrite particles, abrasive, carbon black, binder resin solution (30% by weight of vinyl chloride copolymer resin having potassium sulfonate group and 70% by weight of cyclohexanone) and cyclohexanone so that the solid content becomes 76% by weight. They were mixed and kneaded for 40 minutes using an automatic mortar to obtain a kneaded product.
次いで、上記磁性塗料組成となるように、上記混練物と、追加の結合剤樹脂溶液（スルホン酸ナトリウム基を有するポリウレタン樹脂３０重量％、溶剤（メチルエチルケトン：トルエン＝１：１）７０重量％）、シクロヘキサノン、メチルエチルケトン及びトルエン１．５ｍｍφガラスビーズ９５ｇと共に１４０ｍｌガラス瓶に添加し、ペイントシェーカーで６時間混合・分散を行って非磁性塗料組成物を得た。その後、潤滑剤及び硬化剤を加え、更に、ペイントシェーカーで１５分間混合・分散した後、３μｍの平均孔径を有するフィルターを用いてろ過し、磁気記録層用磁性塗料を調整した。 Next, the kneaded product and an additional binder resin solution (30% by weight of a polyurethane resin having a sodium sulfonate group, 70% by weight of a solvent (methyl ethyl ketone: toluene = 1: 1)) so that the magnetic coating composition is obtained, The mixture was added to a 140 ml glass bottle together with 95 g of cyclohexanone, methyl ethyl ketone and toluene 1.5 mmφ glass beads, and mixed and dispersed for 6 hours with a paint shaker to obtain a nonmagnetic coating composition. Thereafter, a lubricant and a curing agent were added, and further mixed and dispersed for 15 minutes with a paint shaker, followed by filtration using a filter having an average pore diameter of 3 μm to prepare a magnetic coating material for a magnetic recording layer.
上記磁気記録層用塗料を、乾燥後の厚さが１．５μｍになるよう前記非磁性下地層の上に塗布した後、磁場中において配向・乾燥した。その後、６０℃で２４時間硬化反応を行い、１２．７ｍｍ幅にスリットして磁気記録媒体を得た。 The magnetic recording layer coating composition was applied on the nonmagnetic underlayer so that the thickness after drying was 1.5 μm, and then oriented and dried in a magnetic field. Thereafter, a curing reaction was performed at 60 ° C. for 24 hours, and a magnetic recording medium was obtained by slitting to a width of 12.7 mm.
得られた磁気記録媒体は、保磁力Ｈｃが１９７．９ｋＡ／ｍ、Ｂｒ／Ｂｍが０．８１、保磁力分布ＳＦＤが０．５６、光沢度が１７７％、表面粗度Ｒａが１０．１ｎｍであった。 The obtained magnetic recording medium had a coercive force Hc of 197.9 kA / m, a Br / Bm of 0.81, a coercive force distribution SFD of 0.56, a glossiness of 177%, and a surface roughness Ra of 10.1 nm. there were.
前記実施例１−１及び実施例２−１に従って六方晶フェライト粒子粉末及び磁気記録媒体を作製した。各製造条件及び得られた六方晶フェライト粒子粉末及び磁気記録媒体の諸特性を示す。 A hexagonal ferrite particle powder and a magnetic recording medium were prepared according to Example 1-1 and Example 2-1. Various production conditions and various properties of the obtained hexagonal ferrite particle powder and magnetic recording medium are shown.
実施例１−２〜１−３及び比較例１−１：
六方晶フェライト粒子の前駆体の生成反応及び前駆体の焼成における条件を種々変更することにより、六方晶フェライト粒子粉末を得た。
Examples 1-2 to 1-3 and Comparative Example 1-1
Hexagonal ferrite particle powders were obtained by variously changing the conditions for the formation reaction of the precursors of the hexagonal ferrite particles and the firing of the precursors.
このときの製造条件を表１に、得られた六方晶フェライト粒子粉末の諸特性を表２に示す。 The production conditions at this time are shown in Table 1, and various properties of the obtained hexagonal ferrite particle powder are shown in Table 2.
＜磁気記録媒体の製造＞
実施例２−２〜２−３及び比較例２−１：
六方晶フェライト粒子粉末の種類を種々変化させた以外は、前記実施例２−１の磁気記録媒体の作製方法に従って磁気テープを製造した。
<Manufacture of magnetic recording media>
Examples 2-2 to 2-3 and Comparative Example 2-1
A magnetic tape was produced according to the method for producing a magnetic recording medium of Example 2-1 except that the type of hexagonal ferrite particle powder was variously changed.
得られた磁気テープの諸特性を表３に示す。 Table 3 shows various characteristics of the obtained magnetic tape.
本発明に係る水熱合成法による六方晶フェライト粒子粉末の製造法は、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下の微細な六方晶フェライト粒子粉末を工業的に有利に提供できるので、高密度磁気記録媒体の磁性粒子粉末の製造法として好適である。 The method for producing hexagonal ferrite particle powder by the hydrothermal synthesis method according to the present invention can industrially advantageously provide fine hexagonal ferrite particle powder having an average plate surface diameter of more than 20.5 nm and not more than 30 nm. It is suitable as a method for producing magnetic particle powder for high-density magnetic recording media.
本発明に係る製造法によって得られた六方晶フェライト粒子粉末は、平均板面径が２０．５ｎｍを超えて３０ｎｍ以下であると共に、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の範囲にあることから分散性に優れているため、高密度磁気記録媒体の磁性粒子粉末として好適である。
The hexagonal ferrite particle powder obtained by the production method according to the present invention has an average plate surface diameter of more than 20.5 nm and 30 nm or less, and an average plate surface diameter (L) and a BET specific surface area value (SSA). Since it is in a specific range and has excellent dispersibility, it is suitable as a magnetic particle powder for high-density magnetic recording media.
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