JP2011018423A - Hexagonal ferrite particle powder for magnetic recording medium - Google Patents

Hexagonal ferrite particle powder for magnetic recording medium Download PDF

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JP2011018423A
JP2011018423A JP2009163970A JP2009163970A JP2011018423A JP 2011018423 A JP2011018423 A JP 2011018423A JP 2009163970 A JP2009163970 A JP 2009163970A JP 2009163970 A JP2009163970 A JP 2009163970A JP 2011018423 A JP2011018423 A JP 2011018423A
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hexagonal ferrite
particle powder
ferrite particle
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magnetic recording
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JP5403242B2 (en
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Shinji Horie
真司 堀江
Angyoku Sho
安玉 章
Hideji Mitsui
秀治 満井
Hiroko Morii
弘子 森井
Kazuyuki Hayashi
一之 林
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Toda Kogyo Corp
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Abstract

PROBLEM TO BE SOLVED: To provide hexagonal ferrite particle powders highly dispersible in magnetic paint and capable of reducing noise of the magnetic recording medium more.SOLUTION: The hexagonal ferrite particle powders for a magnetic medium is prepared in a manner that an average plate surface diameter (L) among hexagonal ferrite particle powders is 10 to 20.5 nm, and a relationship between the average plate surface diameter (L) and a BET specific surface area value (SSA) is represented by following expression: (1) SSA(m/g)≥-2.3×L(nm)+127.

Description

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.

特開2006−5299号公報JP 2006-5299 A 特開平2−9723号公報Japanese Patent Laid-Open No. 2-9723 特開平7−172839号公報JP-A-7-172839 特開2007−91517号公報JP 2007-91517 A

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)(m/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(m/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10〜20nmであって、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)(m/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(m/g) ≧ −2.3×L(nm)+127 ・・・ (1)
That is, in the present invention, the average plate surface diameter (L) of the hexagonal ferrite particle powder is 10 to 20 nm, and the average plate surface diameter (L) (nm) of the hexagonal ferrite particle powder and the BET specific surface area value ( SSA) (m 2 / g) is a hexagonal ferrite particle powder for magnetic recording media characterized by the following formula (1) (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)(m/g)が下記式(1)の関係にあることを特徴とする。
SSA(m/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)(m/g)との関係は下記式(1)で表される。
SSA(m/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170m/gであることが好ましく、より好ましくは160m/g、更により好ましくは150m/gである。BET比表面積値が170m/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40〜70Am/kgが好ましく、より好ましくは45〜70Am/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 “General X-ray fluorescence analysis rules” of JIS K0119. 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 a magnetic tape was obtained by slitting to a width of 12.7 mm.

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>
BaCl・2HO 0.798mol、FeCl・6HO 6.00mol、NiCl 0.18mol、TiCl 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BaCl・2HO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88.8m/gであり、保磁力値(Hc)は165.6kA/m、飽和磁化(σs)は46.5Am/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:
BaCl ・2H O 0.08mol、FeCl/6HO 0.60mol、NiCl 0.024mol、TiCl 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BaCl・2HO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 carried out 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:
BaCO 24.7mmol、HBO 34.1mmol、Fe 19.8mmol、Co 0.44mmol、ZnO 1.12mmol、Nb 0.28mmol、ZrO 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Bを溶解した。次いで、これらのBaO及びB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).

BaCl・2HO 2mmol、FeCl・6HO 22.7mmol、CoCl・6HO 0.56mmol、ZnCl 0.50mmol、Nb(NO 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) at 22 ° C., the reverse micelle solution (II) was added at 22 ° C. over 3 minutes, and magnetic 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CaCl・6HOを純水に溶解したものを添加し、次いで、NHOHで中和し、六方晶フェライト組成物粒子表面にCa(OH)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.

Figure 2011018423
Figure 2011018423

<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.

Figure 2011018423
Figure 2011018423

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)

六方晶フェライト粒子粉末の平均板面径(L)が10〜20nmであって、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)(m/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。
SSA(m/g) ≧ −2.3×L(nm)+127 ・・・ (1)
The hexagonal ferrite particle powder has an average plate surface diameter (L) of 10 to 20 nm, and the hexagonal ferrite particle powder has an average plate surface diameter (L) (nm) and a BET specific surface area value (SSA) (m 2 / A hexagonal ferrite particle powder for magnetic recording media, wherein g) is in the relationship of the following formula (1):
SSA (m 2 /g)≧−2.3×L (nm) +127 (1)
保磁力(Hc)が95.5kA/m以上であることを特徴とする請求項1記載の磁気記録媒体用六方晶フェライト粒子粉末。 2. The hexagonal ferrite particle powder for magnetic recording media according to claim 1, wherein the coercive force (Hc) is 95.5 kA / m or more.
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JP2012203956A (en) * 2011-03-25 2012-10-22 Fujifilm Corp Method of manufacturing hexagonal ferrite magnetic powder, magnetic recording medium and method of manufacturing the same
JP2014081986A (en) * 2012-09-28 2014-05-08 Fujifilm Corp Manufacturing method of hexagonal ferrite magnetic particles, hexagonal ferrite magnetic particles obtained by manufacturing method, and use of manufacturing method and hexagonal ferrite magnetic particles

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JP2012203956A (en) * 2011-03-25 2012-10-22 Fujifilm Corp Method of manufacturing hexagonal ferrite magnetic powder, magnetic recording medium and method of manufacturing the same
US8840802B2 (en) 2011-03-25 2014-09-23 Fujifilm Corporation Method of manufacturing hexagonal ferrite magnetic powder, magnetic recording medium and method of manufacturing the same
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JP2014081986A (en) * 2012-09-28 2014-05-08 Fujifilm Corp Manufacturing method of hexagonal ferrite magnetic particles, hexagonal ferrite magnetic particles obtained by manufacturing method, and use of manufacturing method and hexagonal ferrite magnetic particles
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