JP5403242B2 - Hexagonal ferrite particles for magnetic recording media - Google Patents
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本発明は、磁気記録媒体用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、平均板面径（Ｌ）が１０〜２０ｎｍであって、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の関係を有する、分散性に優れた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 a hexagonal ferrite particle powder for a magnetic recording medium. Specifically, the average plate surface diameter (L) is 10 to 20 nm, the average plate surface diameter (L) and the BET specific surface area value (SSA). ) Has a specific relationship and relates to a hexagonal ferrite particle powder excellent in dispersibility.
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求められている。 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 more advantageous the noise reduction. Therefore, the particle size of the magnetic particle powder used for the magnetic recording medium is required to be as small as possible.
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.
六方晶フェライト粒子粉末の製法としては、所望のフェライト組成になるように混合した原材料とガラス形成物質を溶融し、急冷して非晶質体とし、次いで再加熱処理した後、洗浄・粉砕して六方晶フェライト粒子粉末を得るガラス結晶化法（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水熱合成法（特許文献２）、所望のフェライト組成の金属塩溶液をアルカリで中和し、得られた鉄塩とバリウム塩の共沈物を水洗・乾燥した後８００℃で熱処理し、粉砕して六方晶フェライト粒子粉末を得る共沈−焼成法（特許文献３）及び共沈物の形成を逆ミセル法により行った共沈−焼成法（特許文献４）等が知られている。 The method for producing hexagonal ferrite particle powder is to melt the raw material and glass-forming substance mixed so as to have a desired ferrite composition, rapidly cool to an amorphous body, and then reheat, wash and grind. Glass crystallization method to obtain hexagonal ferrite particle powder (Patent Document 1), alkaline suspension of desired ferrite composition is liquid phase heated above 100 ° C, washed and dried, then heat treated at around 900 ° C and pulverized Hydrothermal synthesis method to obtain hexagonal ferrite particle powder (Patent Document 2), metal salt solution of desired ferrite composition was neutralized with alkali, and the resulting coprecipitate of iron salt and barium salt was washed with water and dried Thereafter, heat treatment at 800 ° C. and pulverization to obtain hexagonal ferrite particles powder (Patent Document 3) and coprecipitation-firing method in which the coprecipitate is formed by the reverse micelle method (Patent Document 4) Etc. are known That.
平均板面径（Ｌ）が１０〜２０ｎｍであると共に、平均板面径（Ｌ）（ｎｍ）とＢＥＴ比表面積値（ＳＳＡ）（ｍ２／ｇ）が下記式（１）の関係にある磁気記録媒体用六方晶フェライト粒子粉末は未だ得られていない。
ＳＳＡ（ｍ２／ｇ） ≧ −２．３×Ｌ（ｎｍ）＋１２７ ・・・ （１）
The average plate surface diameter (L) is 10 to 20 nm, and the average plate surface diameter (L) (nm) and BET specific surface area value (SSA) (m 2 / g) are in the relationship of the following formula (1). A hexagonal ferrite particle powder for recording media has not yet been obtained.
SSA (m 2 /g)≧−2.3×L (nm) +127 (1)
即ち、前出特許文献１〜４に記載の六方晶フェライト粒子粉末は、いずれも、平均板面径（Ｌ）が１０〜２０ｎｍであると共に、本発明が好ましいとする平均板面径（Ｌ）に対するＢＥＴ比表面積値（ＳＳＡ）の関係を満たしていない。 That is, the hexagonal ferrite particle powders described in the aforementioned Patent Documents 1 to 4 each have an average plate surface diameter (L) of 10 to 20 nm and an average plate surface diameter (L) that the present invention is preferable. The BET specific surface area value (SSA) is not satisfied.
そこで、本発明は、平均板面径（Ｌ）が１０〜２０ｎｍであって、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の関係を有する、分散性に優れた六方晶フェライト粒子粉末を得ることを技術的課題とする。 Accordingly, the present invention provides a hexagonal crystal having excellent dispersibility, in which the average plate surface diameter (L) is 10 to 20 nm, and the average plate surface diameter (L) and the BET specific surface area value (SSA) have a specific relationship. Obtaining ferrite particle powder is a technical problem.
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、六方晶フェライト粒子粉末の平均板面径（Ｌ）が１２．８７〜２０ｎｍであって、ＢＥＴ比表面積値（ＳＳＡ）が９７．４ｍ２／ｇ以下であり、該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）が下記式（１）の関係にあることを特徴とする磁気記録媒体用六方晶フェライト粒子粉末である（本発明１）。
ＳＳＡ（ｍ２／ｇ） ≧ −２．３×Ｌ（ｎｍ）＋１２７ ・・・ （１）
That is, according to the present invention, the hexagonal ferrite particle powder has an average plate surface diameter (L) of 12.87 to 20 nm and a BET specific surface area value (SSA) of 97.4 m 2 / g or less. The hexagonal ferrite for magnetic recording media, characterized in that the average plate surface diameter (L) (nm) and the BET specific surface area value (SSA) (m 2 / g) of the ferrite particle powder are in the relationship of the following formula (1): It is a particle powder (Invention 1).
SSA (m 2 /g)≧−2.3×L (nm) +127 (1)
また、本発明は、保磁力（Ｈｃ）が９５．５ｋＡ／ｍ以上であることを特徴とする本発明１の磁気記録媒体用六方晶フェライト粒子粉末である（本発明２）。 Further, the present invention is the hexagonal ferrite particle powder for magnetic recording media of the present invention 1 (Invention 2), wherein the coercive force (Hc) is 95.5 kA / m or more.
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、平均板面径（Ｌ）が１０〜２０ｎｍであって、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の関係にあることによって、磁性塗料中における分散性に優れると共に、これを磁気記録媒体の磁性粒子粉末として用いた場合には、磁気記録媒体のノイズをより低減できるため、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 for magnetic recording media according to the present invention has an average plate surface diameter (L) of 10 to 20 nm, and the average plate surface diameter (L) and the BET specific surface area value (SSA) have a specific relationship. In addition to being excellent in dispersibility in the magnetic coating material, and when used as a magnetic particle powder of a magnetic recording medium, noise of the magnetic recording medium can be further reduced, so that the magnetic particle powder of a high-density magnetic recording medium It is suitable as.
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、本発明に係る磁気記録媒体用六方晶フェライト粒子粉末について述べる。 First, the hexagonal ferrite particle powder for magnetic recording media 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、平均板面径（Ｌ）が１０〜２０ｎｍであって、平均板面径（Ｌ）（ｎｍ）とＢＥＴ比表面積値（ＳＳＡ）（ｍ２／ｇ）が下記式（１）の関係にあることを特徴とする。
ＳＳＡ（ｍ２／ｇ） ≧ −２．３×Ｌ（ｎｍ）＋１２７ ・・・ （１）
The hexagonal ferrite particle powder for magnetic recording media according to the present invention has an average plate surface diameter (L) of 10 to 20 nm, an average plate surface diameter (L) (nm) and a BET specific surface area value (SSA) (m 2 / g) is in the relationship of the following formula (1).
SSA (m 2 /g)≧−2.3×L (nm) +127 (1)
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、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、Ｓ、Ｓｃ、Ｓｂ、Ｙ、Ｒｈ、Ｐｄ、Ｎｄ、Ｎｂ、Ｂ、Ｐ、Ｇｅ、Ａｌ、Ａｇ、Ａｕ、Ｒｕ、Ｐｒ、Ｂｉ、Ｗ、Ｒｅ、Ｔｅ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 for magnetic recording media according to the present invention is a magnetoplumbite type (M type) ferrite fine particle powder or W type ferrite fine particle containing one or more elements selected from Ba, Sr and Ca. It is a powder or a 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, S, Sc, Sb, Y, Rh, Pd, and Nd. Nb, B, P, Ge, Al, Ag, Au, Ru, Pr, Bi, W, Re, Te, or the like can be used alone or in combination.
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の平均板面径は１０〜２０ｎｍであり、好ましくは１１〜２０ｎｍ、より好ましくは１２〜２０ｎｍである。六方晶フェライト粒子粉末の平均板面径が２０ｎｍを超える場合には、粒子サイズが大きいため、粒子性ノイズをより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１０ｎｍ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 particles for magnetic recording media according to the present invention is 10 to 20 nm, preferably 11 to 20 nm, and more preferably 12 to 20 nm. When the average plate surface diameter of the hexagonal ferrite particle powder exceeds 20 nm, the particle size is large, so that it is difficult to reduce the particulate noise, and it is difficult to obtain a magnetic recording medium having a high C / N ratio. It becomes. Moreover, when the average plate surface diameter is 10 nm or less, the influence of thermal fluctuation accompanying the miniaturization of the magnetic particle powder becomes large, which is not preferable.
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 (average plate surface diameter to average thickness) (hereinafter referred to as “plate ratio”) of the hexagonal ferrite particles for magnetic recording media according to the present invention is preferably 1.5 to 10.0, More preferably, it is 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.
本発明に係る磁気記録媒体用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。
ＳＳＡ（ｍ２／ｇ） ≧ −２．３×Ｌ（ｎｍ）＋１２７ ・・・ （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 particles for magnetic recording media according to the present invention is expressed by the following formula (1). The
SSA (m 2 /g)≧−2.3×L (nm) +127 (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。 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.
本発明に係る磁気記録媒体用磁性微粒子粉末のＢＥＴ比表面積値の下限値は、前述の式（１）で表される値である。また、その上限値は１７０ｍ２／ｇであることが好ましく、より好ましくは１６０ｍ２／ｇ、更により好ましくは１５０ｍ２／ｇである。ＢＥＴ比表面積値が１７０ｍ２／ｇ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。 The lower limit value of the BET specific surface area value of the magnetic fine particle powder for magnetic recording media according to the present invention is a value represented by the above-mentioned formula (1). Moreover, it is preferable that the upper limit is 170 m < 2 > / g, More preferably, it is 160 m < 2 > / g, More preferably, it is 150 m < 2 > / g. When the BET specific surface area value exceeds 170 m 2 / g, aggregation is likely to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in the vehicle during the production of the magnetic coating material is reduced.
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。 As for the magnetic properties of the hexagonal ferrite particles for magnetic recording media 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. The saturation magnetization value is preferably 40 to 70 Am 2 / kg, more preferably 45 to 70 Am 2 / kg.
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、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。 The hexagonal ferrite particle powder for magnetic recording media according to the present invention, if necessary, the surface of the hexagonal ferrite particle powder is made of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. You may coat | cover with the 1 type (s) or 2 or more types of selected compound (henceforth "aluminum hydroxide 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.
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を得るための製造法としては、所望のフェライト組成になるように混合した原材料とガラス形成物質を溶融し、急冷して非晶質体とし、次いで再加熱処理した後、洗浄・粉砕して六方晶フェライト粒子粉末を得るガラス結晶化法、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水熱合成法、所望のフェライト組成の金属塩溶液をアルカリで中和し、得られた鉄塩とバリウム塩の共沈物を水洗・乾燥した後８００℃で熱処理し、粉砕して六方晶フェライト粒子粉末を得る共沈−焼成法等があるが、前述の特性を満たすものであれば特に限定されない。 As a manufacturing method for obtaining a hexagonal ferrite particle powder for magnetic recording media according to the present invention, the raw material and the glass-forming substance mixed so as to have a desired ferrite composition are melted and rapidly cooled to an amorphous body, Next, after reheating treatment, glass crystallization method to obtain hexagonal ferrite particle powder by washing and pulverizing, liquid phase heating of alkaline suspension of desired ferrite composition at 100 ° C. or higher, washing and drying, 900 ° C. Hydrothermal synthesis method to obtain hexagonal ferrite particle powder by heat treatment before and after grinding, neutralize metal salt solution of desired ferrite composition with alkali, wash the resulting iron salt and barium salt coprecipitate with water There is a coprecipitation-firing method in which, after drying, heat treatment at 800 ° C. and pulverization to obtain hexagonal ferrite particle powder, there is no particular limitation as long as it satisfies the aforementioned characteristics.
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 the average thickness of the hexagonal ferrite particle powder were obtained by taking a photograph of the particles using a transmission electron microscope and measuring the plate surface diameter and thickness of each of 360 or more particles using the photograph. The average plate surface diameter and average thickness of the particles are shown by the average value. 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.
比表面積値は、「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 value was represented by a 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 JIS K0119 “General X-ray fluorescence analysis rules” did.
六方晶フェライト粒子粉末の磁気特性は、「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。 The magnetic properties of the hexagonal ferrite particle powder 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.
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の磁気記録媒体における特性を評価・確認するため、以下に示す方法で磁気テープを作製し評価した。 In order to evaluate and confirm the characteristics of the hexagonal ferrite particles for magnetic recording media according to the present invention in the magnetic recording media, magnetic tapes were prepared and evaluated by the following methods.
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。
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. , Cyclohexanone, methyl ethyl ketone and 95 g of toluene 1.5 mmφ glass beads were added to a 140 ml glass bottle 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 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テープを得た。 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 slitting to a width of 12.7 mm gave a magnetic tape.
磁気テープの磁気特性のうち保磁力値Ｈｃと角形比Ｂｒ／Ｂｍ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。 Among the magnetic properties of the magnetic tape, the coercive force value Hc and the squareness ratio Br / Bm were measured using an “oscillating sample magnetometer VSM SSM-5-15” (manufactured by Toei Kogyo Co., Ltd.) and an external magnetic field of 1193.7 kA / m. It measured on condition of this.
磁気テープの磁気特性のうち保磁力分布ＳＦＤ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、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。 Among the magnetic properties of the magnetic tape, the coercive force distribution SFD has a range of 0 to 397.9 kA / m applied magnetic field using “vibrating sample magnetometer VSM SSM-5-15” (manufactured by Toei Kogyo Co., Ltd.). Then, the sweep speed was 79.6 (kA / m) / min, and the sweep speed was measured at 397.9 (kA / m) / min in the range of 397.9 to 1,193.7 kA / m.
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.).
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%.
磁気テープの塗膜の表面粗度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。 The surface roughness Ra of the coating film of the magnetic tape was determined by measuring the center line average roughness of the coating film using “ZYGO NewView 600S” (manufactured by ZYGO Corporation).
磁気テープの電磁変換特性は、ドラムテスターを用い、記録ヘッドにはＭＩＧヘッドを、再生用ヘッドにはＭＲヘッドを用いて測定を行った。ヘッドと磁気テープとの相対速度は２．５ｍ／ｓｅｃとし、記録周波数１０ＭＨｚにおける再生信号出力（Ｃ）及び記録周波数９ＭＨｚにおける出力をノイズ信号出力（Ｎ）を、それぞれ後出参考例２−１を０ｄＢ（基準テープ）として、基準テープに対する相対値として求めた。またＣ／Ｎはこれら再生信号出力（Ｃ）とノイズ信号出力（Ｎ）を用いて示した。 The electromagnetic conversion characteristics of the magnetic tape were measured using a drum tester, a MIG head as a recording head, and an MR head as a reproducing head. The relative speed between the head and the magnetic tape is 2.5 m / sec. The reproduction signal output (C) at a recording frequency of 10 MHz and the output at a recording frequency of 9 MHz are the noise signal output (N). The relative value with respect to the reference tape was determined as 0 dB (reference tape). C / N is shown using these reproduction signal output (C) and noise signal output (N).
＜実施例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 ０．７９８ｍｏｌ、ＦｅＣｌ３・６Ｈ２Ｏ ６．００ｍｏｌ、ＮｉＣｌ２ ０．１８ｍｏｌ、ＴｉＣｌ４ ０．１８ｍｏｌに純水を加えて溶解し、７Ｌの混合溶液を調製した。次いで、１８．５５ｍｏｌ／ＬのＮａＯＨ水溶液５Ｌを攪拌させながら前記混合溶液を２００ｍＬ／ｍｉｎ．の流量でＮａＯＨ水溶液中に添加した後、８０℃で６時間反応を行った。次に、純水を用いて十分に水洗し、共沈物を含む１０Ｌのスラリーとした後、フラックスとしてＢａＣｌ２・２Ｈ２Ｏを前記スラリー１Ｌに対して１００ｇ添加し、ろ過・乾燥して共沈物を得た。
<Example 1: Production of hexagonal ferrite particle powder for magnetic recording medium>
Pure water was added and dissolved in 0.798 mol of BaCl 2 · 2H 2 O, 6.00 mol of FeCl 3 · 6H 2 O, 0.18 mol of NiCl 2 and 0.18 mol of TiCl 4 to prepare a 7 L mixed solution. Next, while stirring 5 L of 18.55 mol / L NaOH aqueous solution, the mixed solution was stirred at 200 mL / min. Was added to an aqueous NaOH solution at a flow rate of 80 ° C. and then reacted at 80 ° C. for 6 hours. Next, after sufficiently washing with pure water to make a 10 L slurry containing coprecipitate, 100 g of BaCl 2 · 2H 2 O as a flux is added to 1 L of the slurry, filtered and dried, I got a deposit.
次いで、得られた共沈物を空気雰囲気下、７２０℃の温度で４時間焼成し、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、塩酸を用いてｐＨ値を２に調製して６０分保持して酸処理を行い、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の六方晶フェライト粒子粉末を得た。 Subsequently, the obtained coprecipitate was baked at a temperature of 720 ° C. for 4 hours in an air atmosphere, and 1 L of pure water was added to the obtained baked product to obtain a dispersed slurry. The obtained slurry was adjusted to pH value 2 with hydrochloric acid and maintained for 60 minutes for acid treatment, adjusted to pH value 5 with aqueous sodium hydroxide solution, washed with water, filtered, dried, By grinding, the hexagonal ferrite particle powder of Example 1 was obtained.
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１８．９ｎｍ、平均厚みは５．８ｎｍ、板状比は３．３、ＢＥＴ比表面積値（実測値）は８８．８ｍ２／ｇであり、保磁力値（Ｈｃ）は１６５．６ｋＡ／ｍ、飽和磁化（σｓ）は４６．５Ａｍ２／ｋｇであった。 The obtained hexagonal ferrite particle powder has a plate shape, an average plate surface diameter of 18.9 nm, an average thickness of 5.8 nm, a plate ratio of 3.3, and a BET specific surface area value (actual measurement value) of 88.8 m. The coercive force value (Hc) was 165.6 kA / m, and the saturation magnetization (σs) was 46.5 Am 2 / kg.
実施例２：
ＢａＣｌ２ ・２Ｈ２ Ｏ ０．０８ｍｏｌ、ＦｅＣｌ３／６Ｈ２Ｏ ０．６０ｍｏｌ、ＮｉＣｌ２ ０．０２４ｍｏｌ、ＴｉＣｌ４ ０．０２４ｍｏｌ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ＮａＯＨ水溶液中に添加し、オートクレーブを用いて１５０℃で６時間反応を行った後、室温まで冷却した。反応溶液を「超音波ホモジナイザー ＳｏｎｉｆｉｅｒＩＩ ｍｏｄｅｌ ４５０Ｄ」（ＢＲＡＮＳＯＮ株式会社製）を用いて１０分間攪拌後、純水を用いて十分に水洗し、六方晶フェライト粒子の種晶を含む１Ｌのスラリーとした後、フラックスとしてＢａＣｌ２・２Ｈ２Ｏを前記スラリー１Ｌに対して１００ｇ添加し、ろ過・乾燥して六方晶フェライト粒子の種晶を得た。
Example 2:
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 0.024 mol, TiCl 4 0.024 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 1, and the reaction was performed at 150 ° C. for 6 hours using an autoclave, and then cooled to room temperature. After stirring the reaction solution for 10 minutes using “Ultrasonic Homogenizer Sonifier II model 450D” (manufactured by BRANSON Co., Ltd.) and thoroughly washing with pure water to obtain a 1 L slurry containing seed crystals of hexagonal ferrite particles Then, 100 g of BaCl 2 .2H 2 O as a flux was added to 1 L of the slurry, and filtered and dried to obtain seed crystals of hexagonal ferrite particles.
次いで、得られた六方晶フェライト粒子の種晶を空気雰囲気下、７２０℃の温度で４時間焼成し、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、塩酸を用いてｐＨ値を２に調製して６０分保持して酸処理を行い、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２の六方晶フェライト粒子粉末を得た。得られた六方晶フェライト粒子粉末の諸特性を表１に示す。 Subsequently, the seed crystals of the obtained hexagonal ferrite particles were fired in an air atmosphere at a temperature of 720 ° C. for 4 hours, and 1 L of pure water was added to the fired product to obtain a dispersed slurry. The obtained slurry was adjusted to pH value 2 with hydrochloric acid and maintained for 60 minutes for acid treatment, adjusted to pH value 5 with aqueous sodium hydroxide solution, washed with water, filtered, dried, The hexagonal ferrite particle powder of Example 2 was obtained by pulverization. Table 1 shows various properties of the obtained hexagonal ferrite particle powder.
実施例３：
ＢａＣＯ３ ２４．７ｍｍｏｌ、Ｈ３ＢＯ３ ３４．１ｍｍｏｌ、Ｆｅ２Ｏ３ １９．８ｍｍｏｌ、Ｃｏ３Ｏ４ ０．４４ｍｍｏｌ、ＺｎＯ １．１２ｍｍｏｌ、Ｎｂ２Ｏ５ ０．２８ｍｍｏｌ、ＺｒＯ２ ０．１４ｍｍｏｌを十分に混合し、白金ルツボに混合原料を入れて、１３３０℃で加熱溶融した後、（均質化した）溶融物を急冷（圧延）し、非晶質体を作製した。得られた非晶質体を６００℃で３時間保持して六方晶フェライト結晶を析出させた。析出物を粉砕した後、１０％の酢酸溶液中で、溶液温度を８０℃以上に制御しながら、４時間攪拌し酸処理を行い、ＢａＯ及びＢ２Ｏ３を溶解した。次いで、これらのＢａＯ及びＢ２Ｏ３成分並びに酸成分を除去するため水洗を繰り返した後、スラリーを乾燥させ、実施例３の六方晶フェライト粒子粉末を得た。得られた六方晶フェライト粒子粉末の諸特性を表１に示す。
Example 3:
BaCO 3 24.7mmol, H 3 BO 3 34.1mmol, Fe 2 O 3 19.8mmol, Co 3 O 4 0.44mmol, ZnO 1.12mmol, Nb 2 O 5 0.28mmol, ZrO 2 0.14mmol enough The mixed raw material was put into a platinum crucible, heated and melted at 1330 ° C., and then the (homogenized) melt was quenched (rolled) to produce an amorphous body. The obtained amorphous body was kept at 600 ° C. for 3 hours to precipitate hexagonal ferrite crystals. After pulverizing the precipitate, acid treatment was performed by stirring for 4 hours in a 10% acetic acid solution while controlling the solution temperature at 80 ° C. or higher to dissolve BaO and B 2 O 3 . Subsequently, water washing was repeated to remove these BaO and B 2 O 3 components and the acid component, and then the slurry was dried to obtain hexagonal ferrite particle powder of Example 3. Table 1 shows various properties of the obtained hexagonal ferrite particle powder.
実施例４：
実施例１で得られた共沈物の焼成温度を６９０℃とし、３．５時間焼成した以外は実施例１と同様にして実施例４の六方晶フェライト粒子粉末を得た。得られた六方晶フェライト粒子粉末の諸特性を表１に示す。
Example 4:
The hexagonal ferrite particle powder of Example 4 was obtained in the same manner as in Example 1 except that the coprecipitate obtained in Example 1 was fired at 690 ° C. and fired for 3.5 hours. Table 1 shows various properties of the obtained hexagonal ferrite particle powder.
実施例５：
実施例１の六方晶フェライト粒子粉末２００ｇと水１５００ｍｌとを用いて分散スラリーを調整し、水酸化ナトリウム水溶液を添加してｐＨ値を９とした後、該スラリーに水を加えスラリー濃度を９８ｇ／Ｌとした。このスラリー１５０ｌを加熱して６０℃とし、このスラリー中に３号水ガラス ９．８ｍＬ（六方晶フェライト粒子粉末に対してＳｉ換算で０．９重量％に相当する）を加え、３０分間保持した後、酢酸を用いてｐＨ値を９に調整した。この状態で３０分間保持した後、濾過・水洗・乾燥・粉砕し、粒子表面がケイ素化合物により被覆されている実施例５の六方晶フェライト粒子粉末を得た。得られた六方晶フェライト粒子粉末の諸特性を表１に示す。
Example 5:
A dispersion slurry was prepared using 200 g of the hexagonal ferrite particle powder of Example 1 and 1500 ml of water, and after adding a sodium hydroxide aqueous solution to adjust the pH value to 9, water was added to the slurry to obtain a slurry concentration of 98 g / L. 150 l of this slurry was heated to 60 ° C., and 9.8 mL of No. 3 water glass (corresponding to 0.9% by weight in terms of Si with respect to hexagonal ferrite particle powder) was added to this slurry and held for 30 minutes. Thereafter, the pH value was adjusted to 9 using acetic acid. After maintaining for 30 minutes in this state, filtration, washing with water, drying and pulverization were performed to obtain hexagonal ferrite particle powder of Example 5 in which the particle surface was coated with a silicon compound. Table 1 shows various properties of the obtained hexagonal ferrite particle powder.
比較例１（特開２００７−９１５１７号公報 実施例５に準じた追試実験）：
ＮａＯＨ ８０ｍｍｏｌを純水１６０ｍｌに溶解した水溶液に、エーロゾルＯＴ １０８ｇとデカン８００ｍｌとを混合したアルカン溶液を添加、混合して逆ミセル溶液（Ｉ）を調製した。
Comparative Example 1 (Follow-up test according to Example 5 of JP 2007-91517 A):
An alkane solution in which 108 g of aerosol OT and 800 ml of decane were mixed was added to an aqueous solution in which 80 mmol of NaOH was dissolved in 160 ml of pure water to prepare a reverse micelle solution (I).
ＢａＣｌ２・２Ｈ２Ｏ ２ｍｍｏｌ、ＦｅＣｌ３・６Ｈ２Ｏ ２２．７ｍｍｏｌ、ＣｏＣｌ２・６Ｈ２Ｏ ０．５６ｍｍｏｌ、ＺｎＣｌ２ ０．５０ｍｍｏｌ、Ｎｂ（ＮＯ３）３ ０．２４ｍｍｏｌを純水１４０ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ ５４ｇとデカン５００ｍｌとを混合したアルカン溶液を添加、混合して逆ミセル溶液（ＩＩ）を調製した。 BaCl 2 · 2H 2 O 2 mmol, FeCl 3 · 6H 2 O 22.7 mmol, CoCl 2 · 6H 2 O 0.56 mmol, ZnCl 2 0.50 mmol, Nb (NO 3 ) 3 0.24 mmol were dissolved in 140 ml of pure water. To the aqueous metal salt solution, an alkane solution in which 54 g of aerosol OT and 500 ml of decane were mixed was added and mixed to prepare a reverse micelle solution (II).
逆ミセル溶液（Ｉ）を２２℃で「超音波ホモジナイザー ＳｏｎｉｆｉｅｒＩＩ ｍｏｄｅｌ ４５０Ｄ」（ＢＲＡＮＳＯＮ株式会社製）で高速攪拌しながら、２２℃にした逆ミセル溶液（ＩＩ）を３分間かけて添加し、マグネチックスターラーで８分攪拌した後、５０℃に昇温して３０分間熟成し、室温まで冷却して大気中に取出した。逆ミセルを破壊するために、水５００ｍｌとメタノール５００ｍｌとの混合溶液を添加して水相と油相とに分離し、共沈粒子が分散した油相側を水６００ｍｌとメタノール２００ｍｌとの混合溶液で２回洗浄した後、メタノールを２０００ｍｌ添加して共沈粒子にフロキュレーションを起こさせて沈降させ、上澄み液を除去した後、ヘプタン１００ｍｌを添加して再分散させた。 While the reverse micelle solution (I) was stirred at a high speed with an “ultrasonic homogenizer Sonifier II model 450D” (manufactured by BRANSON Co., Ltd.) at 22 ° C., the reverse micelle solution (II) was added to 22 ° C. over 3 minutes and magnetically added. After stirring for 8 minutes with a stirrer, the temperature was raised to 50 ° C., aged for 30 minutes, cooled to room temperature, and taken out into the atmosphere. In order to destroy the reverse micelle, a mixed solution of 500 ml of water and 500 ml of methanol is added to separate into an aqueous phase and an oil phase, and the oil phase side in which the coprecipitated particles are dispersed is mixed with 600 ml of water and 200 ml of methanol. Then, 2000 ml of methanol was added to cause co-precipitation particles to flocculate and settle. After removing the supernatant, 100 ml of heptane was added and redispersed.
更に、メタノール１０００ｍｌ添加による沈降とヘプタン１００ｍｌ分散との沈降分散を２回繰り返し、メタノールを添加して共沈粒子を沈降させた。上澄みを除去し、次に水１０００ｍｌを添加し分散、沈降、上澄み除去を２回繰り返した。得られた共沈物を純水１Ｌ中に再分散し、０．１モルのＣａＣｌ２・６Ｈ２Ｏを純水に溶解したものを添加し、次いで、ＮＨ４ＯＨで中和し、六方晶フェライト組成物粒子表面にＣａ（ＯＨ）２の被覆を形成した。沈殿物をろ過・水洗し、次いで１２０℃で乾燥した後、乾燥物を粉砕した。 Further, precipitation by adding 1000 ml of methanol and precipitation dispersion of 100 ml of heptane were repeated twice, and methanol was added to precipitate the coprecipitated particles. The supernatant was removed, and then 1000 ml of water was added to disperse, settle and remove the supernatant twice. The coprecipitate obtained was redispersed in 1 L of pure water, 0.1 mol of CaCl 2 · 6H 2 O dissolved in pure water was added, and then neutralized with NH 4 OH, hexagonal crystal A coating of Ca (OH) 2 was formed on the surface of the ferrite composition particles. The precipitate was filtered and washed with water, and then dried at 120 ° C., and then the dried product was pulverized.
粉砕した乾燥物を空気中で６００℃にて加熱し表面被覆物を酸化物とした後、更に７００℃で２時間熱処理し、六方晶フェライト粒子粉末とした。生成物を５％酢酸水溶液に入れ表面被覆物を除去し、比較例１の六方晶フェライト粒子粉末を得た。得られた六方晶フェライト粒子粉末の諸特性を表１に示す。 The pulverized dried product was heated in air at 600 ° C. to convert the surface coating into an oxide, and further heat treated at 700 ° C. for 2 hours to obtain hexagonal ferrite particle powder. The product was placed in a 5% aqueous acetic acid solution to remove the surface coating, and the hexagonal ferrite particle powder of Comparative Example 1 was obtained. Table 1 shows various properties of the obtained hexagonal ferrite particle powder.
＜磁気テープの製造＞
磁気テープ１〜５、比較磁気テープ１：
六方晶フェライト粒子の種類を種々変化させた以外は、前記実施例の磁気テープの作製方法に従って磁気テープを製造した。
<Manufacture of magnetic tape>
Magnetic tape 1-5, comparative magnetic tape 1:
A magnetic tape was manufactured according to the magnetic tape manufacturing method of the above example except that the type of hexagonal ferrite particles was variously changed.
得られた磁気テープの諸特性を表２に示す。 Table 2 shows the characteristics of the obtained magnetic tape.
上記実施例からわかるように、本発明により得られた六方晶フェライト粒子粉末は、平均板面径（Ｌ）が１０〜２０．５ｎｍであって、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の関係にあることによって、磁性塗料中における分散性に優れるため、これらを用いて得られた磁気記録媒体は、ノイズがより低減され、高いＣ／Ｎが得られている。 As can be seen from the above examples, the hexagonal ferrite particle powder obtained by the present invention has an average plate surface diameter (L) of 10 to 20.5 nm, and the average plate surface diameter (L) and BET specific surface area value. When (SSA) is in a specific relationship, the dispersibility in the magnetic paint is excellent, and thus the magnetic recording medium obtained using these has a reduced noise and a high C / N.
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、平均板面径（Ｌ）が１０〜２０．５ｎｍであって、平均板面径（Ｌ）とＢＥＴ比表面積値（ＳＳＡ）が特定の関係にあることによって、磁性塗料中における分散性に優れると共に、これを磁気記録媒体の磁性粒子粉末として用いた場合には、磁気記録媒体のノイズをより低減できるため、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 for magnetic recording media according to the present invention has an average plate surface diameter (L) of 10 to 20.5 nm, and a specific plate surface diameter (L) and BET specific surface area value (SSA) are specific. Due to this relationship, the dispersibility in the magnetic paint is excellent, and when this is used as the magnetic particle powder of the magnetic recording medium, the noise of the magnetic recording medium can be further reduced. Suitable as particle powder.
Claims (2)
ＳＳＡ（ｍ２／ｇ） ≧ −２．３×Ｌ（ｎｍ）＋１２７ ・・・ （１） The hexagonal ferrite particle powder has an average plate surface diameter (L) of 12.87 to 20 nm and a BET specific surface area value (SSA) of 97.4 m 2 / g or less. A hexagonal ferrite particle powder for magnetic recording media, wherein the surface diameter (L) (nm) and the BET specific surface area value (SSA) (m 2 / g) are in the relationship of the following formula (1).
SSA (m 2 /g)≧−2.3×L (nm) +127 (1)
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