JPH1027705A - Iron oxide magnetic powder and magnetic recording medium formed thereof - Google Patents

Iron oxide magnetic powder and magnetic recording medium formed thereof

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Publication number
JPH1027705A
JPH1027705A JP8180577A JP18057796A JPH1027705A JP H1027705 A JPH1027705 A JP H1027705A JP 8180577 A JP8180577 A JP 8180577A JP 18057796 A JP18057796 A JP 18057796A JP H1027705 A JPH1027705 A JP H1027705A
Authority
JP
Japan
Prior art keywords
iron oxide
magnetic
magnetic powder
magnetic recording
recording medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP8180577A
Other languages
Japanese (ja)
Inventor
Setsuko Murakami
節子 村上
Masashi Meguro
政志 目黒
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sony Corp
Original Assignee
Sony Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sony Corp filed Critical Sony Corp
Priority to JP8180577A priority Critical patent/JPH1027705A/en
Publication of JPH1027705A publication Critical patent/JPH1027705A/en
Pending legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To obtain iron oxide magnetic powder which is needle-shaped, excellent in magnetic properties, and lessened in resistance by a method where in Si atoms are added at a specific ratio to Fe, and the ratio Fe<2+> /Fe<3+> is set at a specific value or above, and H2 O is added to the iron oxide magnetic powder at a specific ratio. SOLUTION: 0.4 to 0.7atm% of Si atoms is added to Fe atoms, the ratio Fe<2+> /Fe<3+> is set at 0.12 or above, an 0.1 to 0.7wt.% of H2 O (moisture) is added to iron oxide magnetic powder to lessen it enough in resistance. γ-Fe2 O3 and Co modified-γ-Fe2 O3 are typical of iron oxide magnetic powder. Iron oxide magnetic powder is turned to magnetic paint through the same process as conventional γ-Fe3 O3 , and the magnetic paint is applied onto a non-magnetic support, whereby the non-magnetic support can be lessened enough in surface electric resistance and given magnetic properties adequate for magnetic recording of high density.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【０００１】[0001]

【発明の属する技術分野】本発明は酸化鉄系磁性粉末お
よびこれを用いた磁気記録媒体に関し、さらに詳しく
は、微細で良好な針状性を有するとともに、電気抵抗が
低減された酸化鉄系磁性粉末およびこれを用いた磁気記
録媒体に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron oxide-based magnetic powder and a magnetic recording medium using the same, and more particularly, to an iron oxide-based magnetic powder having fine and good needle-like properties and reduced electric resistance. The present invention relates to a powder and a magnetic recording medium using the same.

【０００２】[0002]

【従来の技術】オーディオ装置、ビデオ装置あるいはコ
ンピュータ装置等に付随する磁気記録装置で用いられる
磁気記録媒体として、磁性粉末、有機バインダおよび各
種添加剤等を有機溶媒に分散、混練して調整される磁性
塗料を、非磁性支持体上に塗布、乾燥することにより形
成される磁気記録層を用いた、いわゆる塗布型の磁気記
録媒体が用いられている。この塗布型の磁気記録媒体
は、生産性、汎用性に優れることから、現在においても
磁気記録媒体の主流を占めている。2. Description of the Related Art As a magnetic recording medium used in a magnetic recording device associated with an audio device, a video device or a computer device, a magnetic powder, an organic binder and various additives are dispersed and kneaded in an organic solvent and adjusted. A so-called coating type magnetic recording medium using a magnetic recording layer formed by applying and drying a magnetic paint on a non-magnetic support is used. Since the coating type magnetic recording medium is excellent in productivity and versatility, it is still the mainstream of magnetic recording media even at present.

【０００３】これらの各種磁気記録装置においては、近
年ますます小型軽量化、高画質化ならびに長時間化等が
要求され、磁気記録媒体に対しても高密度記録化が強く
要望されるようになっている。このためには、磁性粉末
の抗磁力や飽和磁束密度等の磁気特性とともに、個々の
粒子形状の制御が重要である。磁性粉末材料のうち、酸
化鉄系のマグヘマイト（γ−Ｆｅ2 Ｏ3 ）や、これをＣ
ｏ変成したＣｏ−γ−Ｆｅ2 Ｏ3 は、電気抵抗が一般的
に高い。さらに最近では、粒子の焼結を防止し良好な形
状異方性を確保するために、粒子表面にＳｉを１〜２
％、時には数％被着して還元・酸化等の熱処理を施す方
法が一般的である。しかしながらこの方法においては、
Ｓｉは粒子表面で主としてシリカ（ＳｉＯ2 ）として存
在するため、Ｆｅ原子の粒子表面での露出割合が低減
し、絶縁膜で覆われた形となるので、ますます電気抵抗
が上昇する方向である。したがって、これらを用いた塗
布型の磁気記録媒体の表面電気抵抗も高くなる。[0003] In these various magnetic recording apparatuses, in recent years, smaller and lighter, higher image quality and longer time have been demanded, and high density recording has also been strongly demanded for magnetic recording media. ing. For this purpose, it is important to control the shape of each particle as well as the magnetic properties such as the coercive force and the saturation magnetic flux density of the magnetic powder. Among the magnetic powder materials, iron oxide maghemite (γ-Fe 2 O 3 ) and
O-modified Co-γ-Fe 2 O 3 generally has high electric resistance. More recently, in order to prevent sintering of particles and secure good shape anisotropy, Si is applied to the surface of the particles in an amount of 1 to 2 times.
%, And sometimes a few%, and a heat treatment such as reduction and oxidation is performed. However, in this method,
Since Si is mainly present on the particle surface as silica (SiO 2 ), the exposure ratio of Fe atoms on the particle surface is reduced and the particles are covered with an insulating film, so that the electric resistance is further increased. . Therefore, the surface electric resistance of the coating type magnetic recording medium using these also becomes high.

【０００４】磁気記録テープ等の磁気記録媒体の表面電
気抵抗が高いと、走行中にガイドや磁気ヘッド等との摩
擦により帯電し、異物粒子の付着による疵やドロップア
ウトが発生する。また磁気テープがテープガイドや磁気
ドラム等に張り付いて走行不良の原因ともなる。したが
って、エラーレートや変調ノイズ等が少ない高密度記録
を達成するためには、磁気記録媒体の表面電気抵抗を低
減することが不可欠である。If the surface electrical resistance of a magnetic recording medium such as a magnetic recording tape is high, the magnetic recording medium is charged by friction with a guide, a magnetic head, or the like during running, and flaws or dropouts due to adhesion of foreign particles occur. In addition, the magnetic tape sticks to the tape guide, the magnetic drum, or the like, which causes a running failure. Therefore, in order to achieve high-density recording with little error rate and modulation noise, it is essential to reduce the surface electric resistance of the magnetic recording medium.

【０００５】磁気記録媒体の表面電気抵抗を下げる従来
技術として、磁性塗料中にカーボン粉末のような導電性
の非磁性添加物を含有させる方法がある。この方法によ
ると、表面電気抵抗を充分に低減するためには、カーボ
ン粉末を多量に添加する必要があり、磁気記録層中の磁
性粉末の体積分率が下がるため、磁束密度が低下する。
また酸化鉄系磁性粉末自体の電気抵抗を低減する方法と
して、酸化鉄系磁性粉末表面に炭素質被膜を形成する方
法が、例えば特開平３−１５０５号公報に開示されてい
る。しかしながらこの方法も、表面電気抵抗を充分に低
減するためには炭素質被膜を厚く形成する必要があり、
カーボン粉末添加と同様の問題点を有している。As a conventional technique for lowering the surface electric resistance of a magnetic recording medium, there is a method of incorporating a conductive non-magnetic additive such as carbon powder into a magnetic paint. According to this method, in order to sufficiently reduce the surface electric resistance, it is necessary to add a large amount of carbon powder, and the volume fraction of the magnetic powder in the magnetic recording layer decreases, so that the magnetic flux density decreases.
As a method of reducing the electric resistance of the iron oxide-based magnetic powder itself, a method of forming a carbonaceous film on the surface of the iron oxide-based magnetic powder is disclosed in, for example, Japanese Patent Application Laid-Open No. 3-1505. However, this method also requires a thick carbonaceous film in order to sufficiently reduce the surface electric resistance,
It has the same problems as the addition of carbon powder.

【０００６】[0006]

【発明が解決しようとする課題】本発明はかかる従来技
術の問題点に鑑み提案するものであり、微細な磁性粒子
の針状性等の形状と磁気特性に優れるとともに、電気抵
抗の低減された酸化鉄系磁性粉末を提供することを課題
とする。また本発明は、かかる酸化鉄系磁性粉末を用い
ることにより、表面電気抵抗が低減され、磁束密度が低
下することなく、磁気記録層中での磁性粉末の分散が良
好な、高密度磁気記録の分野においてすぐれた電磁変換
特性が得られる磁気記録媒体を提供することをその課題
とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been proposed in which fine magnetic particles are excellent in the shape and magnetic properties such as acicularity and the electric resistance is reduced. An object is to provide an iron oxide-based magnetic powder. In addition, the present invention uses such an iron oxide-based magnetic powder, whereby the surface electric resistance is reduced, the magnetic flux density is not reduced, and the dispersion of the magnetic powder in the magnetic recording layer is good. It is an object of the present invention to provide a magnetic recording medium having excellent electromagnetic conversion characteristics in the field.

【０００７】[0007]

【課題を解決するための手段】本発明の酸化鉄系磁性粉
末は上述の課題を解決するために提案するものであり、
Ｓｉ原子をＦｅ原子に対して０．４ａｔｍ％以上０．７
ａｔｍ％以下含有するとともに、Ｆｅ2+／Ｆｅ3+ イオ
ン比が０．１２以上であり、かつＨ2 Ｏ（水分）を酸化
鉄系磁性粉末に対して０．１ｗｔ％以上０．７ｗｔ％以
下含有することを特徴とする。The iron oxide magnetic powder of the present invention is proposed to solve the above-mentioned problems.
0.4 atom% or more of Si atom to Fe atom 0.7
atm% or less, Fe 2+ / Fe 3+ ion ratio is 0.12 or more, and H 2 O (water) is 0.1 wt% or more and 0.7 wt% or less based on the iron oxide magnetic powder. It is characterized by containing.

【０００８】また本発明の磁気記録媒体は、かかる酸化
鉄系磁性粉末と、有機バインダとを主体とする磁気記録
層を、非磁性支持体上に有することを特徴とする。Further, the magnetic recording medium of the present invention is characterized in that a magnetic recording layer mainly comprising such an iron oxide-based magnetic powder and an organic binder is provided on a non-magnetic support.

【０００９】本発明者らはγ−Ｆｅ3 Ｏ3 等の３価鉄
（Ｆｅ3+）を主体とする酸化鉄系磁性粉末の電気抵抗に
ついて鋭意研究を加えた結果、Ｓｉ原子をＦｅ原子に対
して０．４ａｔｍ％以上０．７ａｔｍ％以下、Ｆｅ2+／
Ｆｅ3+イオン比が０．１２以上、かつＨ2 Ｏ（水分）を
酸化鉄系磁性粉末の０．１ｗｔ％以上０．７ｗｔ％以下
含有する場合に、抵抗値を充分に下げることができるこ
とを見出し、本発明を完成するに至った。本発明が対象
とする酸化鉄系磁性粉末の代表的なものは、γ−Ｆｅ2
Ｏ3 およびＣｏ変成γ−Ｆｅ2 Ｏ3 のいずれかである。
またかかる酸化鉄系磁性粉末を通常のγ−Ｆｅ3 Ｏ3 等
と同様の工程により磁性塗料とし、これを非磁性支持体
上に塗布形成することにより、表面電気抵抗が充分に低
減されるとともに、高密度磁気記録に適した磁気特性を
付与することが可能となった。The present inventors have conducted intensive studies on the electrical resistance of iron oxide-based magnetic powders mainly composed of trivalent iron (Fe 3+ ) such as γ-Fe 3 O 3. As a result, Si atoms were converted to Fe atoms. In contrast, 0.4 atm% or more and 0.7 atm% or less, Fe 2+ /
When the Fe 3+ ion ratio is 0.12 or more and H 2 O (water) is contained in the iron oxide-based magnetic powder in the range of 0.1 wt% to 0.7 wt%, the resistance can be sufficiently reduced. As a result, the present invention has been completed. A typical iron oxide-based magnetic powder targeted by the present invention is γ-Fe 2
O 3 or Co-modified γ-Fe 2 O 3 .
The iron oxide-based magnetic powder is formed into a magnetic paint by the same process as that of ordinary γ-Fe 3 O 3 and the like, and is applied and formed on a non-magnetic support, so that the surface electric resistance is sufficiently reduced and This makes it possible to provide magnetic characteristics suitable for high-density magnetic recording.

【００１０】本発明においては、２価鉄（Ｆｅ2+）が主
に電気伝導に寄与するため、カーボン等の非磁性導電材
料と異なり、酸化鉄系磁性粉末の飽和磁化や磁気記録媒
体の磁束密度が低下する虞れはない。酸化鉄系磁性粉末
の電気抵抗を充分に低減するためには、Ｆｅ2+／Ｆｅ3+
イオン比が０．１２以上であることが好ましい。このＦ
ｅ2+／Ｆｅ3+イオン比の上限は、マグネタイト（Ｆｅ3
Ｏ4 ）のＦｅ2+／Ｆｅ3+イオン比が０．５であるのでこ
の値が目安となるが、マグネタイトそのものは経時安定
性や層間転写等の問題があるので、０．３０以下が好ま
しい。In the present invention, since ferrous iron (Fe 2+ ) mainly contributes to electric conduction, unlike a nonmagnetic conductive material such as carbon, the saturation magnetization of iron oxide-based magnetic powder and the magnetic flux of a magnetic recording medium are different. There is no fear that the density will decrease. In order to sufficiently reduce the electric resistance of the iron oxide-based magnetic powder, Fe 2+ / Fe 3+
Preferably, the ion ratio is 0.12 or more. This F
The upper limit of the e 2+ / Fe 3+ ion ratio is magnetite (Fe 3
Since the Fe 2+ / Fe 3+ ion ratio of O 4 ) is 0.5, this value is a standard. However, since magnetite itself has problems such as stability over time and interlayer transfer, it is preferably 0.30 or less. .

【００１１】Ｆｅ2+／Ｆｅ3+イオン比の制御は、酸化鉄
系磁性粉末製造工程における徐酸化工程を制御すること
により可能となる。一般にγ−Ｆｅ2 Ｏ3 等の酸化鉄系
磁性粉末は、Ｓｉ化合物で表面処理されたα−ＦｅＯＯ
Ｈ、β−ＦｅＯＯＨおよびγ−ＦｅＯＯＨ等のオキシ水
酸化鉄やその脱水酸化物、好ましくはα−ＦｅＯＯＨお
よびγ−ＦｅＯＯＨあるいはその脱水酸化物を加熱水素
還元してＦｅ3 Ｏ4 とした後、空気等の酸化性ガスによ
り徐酸化処理して形成される。この徐酸化工程は比較的
長時間を要する工程であるので、時間管理や酸化性ガス
流量管理等によりＦｅ2+／Ｆｅ3+イオン比を制御するこ
とが可能である。この反対に、完全に酸化されたγ−Ｆ
ｅ2 Ｏ3 をさらに不完全還元することにより、Ｆｅ2+／
Ｆｅ3+イオン比を制御することも可能である。The Fe 2+ / Fe 3+ ion ratio can be controlled by controlling the gradual oxidation step in the iron oxide-based magnetic powder production step. In general, iron oxide-based magnetic powders such as γ-Fe 2 O 3 are formed of α-FeOO surface-treated with a Si compound.
H, β-FeOOH and γ-FeOOH, etc., iron oxyhydroxide and its dehydrated oxide, preferably α-FeOOH and γ-FeOOH or its dehydrated oxide are heated and hydrogen reduced to Fe 3 O 4 , and then air Formed by gradual oxidation with an oxidizing gas such as Since this slow oxidation step requires a relatively long time, the Fe 2+ / Fe 3+ ion ratio can be controlled by time management, oxidizing gas flow rate control, and the like. Conversely, fully oxidized γ-F
By further incomplete reduction of e 2 O 3 , Fe 2+ /
It is also possible to control the Fe 3+ ion ratio.

【００１２】これら原料のオキシ水酸化鉄の形状は最終
生成物である酸化鉄系磁性粉末の粒子形状に反映するの
で、平均長軸長が０．０５〜０．３μｍ、平均軸比（ア
スペクト比）が３〜２０であって、針状、柱状、棒状あ
るいは紡錘形状のものが好ましい。このオキシ水酸化鉄
中には、Ｃｏ、Ｎｉ、Ｃｒ、Ｍｎ、Ｍｇ、Ｓｉ、Ｃａ、
Ｂａ、Ｓｒ、Ｚｎ、Ｔｉ、Ｍｏ、Ａｇ、Ｃｕ、Ｎａ、
Ｋ、Ｌｉ、ＡｌあるいはＺｒ等の元素を含んでいてもよ
い。Since the shape of the iron oxyhydroxide as these raw materials is reflected in the particle shape of the iron oxide magnetic powder as the final product, the average major axis length is 0.05 to 0.3 μm and the average axial ratio (aspect ratio) ) Is from 3 to 20 and is preferably in the shape of a needle, a column, a rod or a spindle. In this iron oxyhydroxide, Co, Ni, Cr, Mn, Mg, Si, Ca,
Ba, Sr, Zn, Ti, Mo, Ag, Cu, Na,
It may contain an element such as K, Li, Al or Zr.

【００１３】本発明の酸化鉄系磁性粉末中のＳｉ原子は
形状保持剤である。先述したように従来粒子表面にＳｉ
を１〜２％、時には数％被着して還元・酸化等の熱処理
を施していたが、この被着量を再検討し可及的に低減す
ることとした。この結果、０．４ａｔｍ％未満では焼結
防止の効果が劣化し、０．７ａｔｍ％を超えると電気抵
抗が許容範囲以上に上昇することを確認した。かかる形
状保持剤は、Ｓｉの可溶性塩、例えば塩化物、硫酸塩、
硝酸塩、あるいは珪酸塩等を原料のオキシ水酸化鉄表面
に被着することにより導入される。すなわち、オキシ水
酸化鉄を水に分散させた懸濁液にＳｉの可溶性塩あるい
はその水溶液を添加して均一に混合し、この後アルカリ
側にｐＨ調整することにより、オキシ水酸化鉄表面に被
着させる。ｐＨ調整にはＮａＯＨやＫＯＨ等の水酸化ア
ルカリ等が用いられる。Ｓｉの可溶性塩を被着したオキ
シ水酸化鉄はろ過、洗浄、粉砕して微細な粉末状とす
る。この後の工程は常法に準じ、まず４００度〜７５０
℃で熱処理し、ヘマタイト（α−Ｆｅ2 Ｏ3 ）とすると
ともに、被着されたＳｉの可溶性塩はシリカとしてα−
Ｆｅ2 Ｏ3 粒子の表層に定着する。この後、Ｈ2 等によ
り還元し、Ｆｅ3 Ｏ4 とし、さらに徐酸化してγ−Ｆｅ
2 Ｏ3 が得られる。かかる多段階の熱処理工程において
も、焼結は有効に防止される。The Si atom in the iron oxide-based magnetic powder of the present invention is a shape-retaining agent. As described above, conventionally, Si
Was subjected to a heat treatment such as reduction and oxidation by 1 to 2%, and sometimes several%, but the amount of the deposition was re-examined to be reduced as much as possible. As a result, it was confirmed that the effect of preventing sintering was deteriorated when the content was less than 0.4 atm%, and that the electrical resistance was increased to an allowable range or more when the content exceeded 0.7 atm%. Such shape-retaining agents include soluble salts of Si, such as chlorides, sulfates,
It is introduced by depositing nitrate or silicate on the surface of the raw material iron oxyhydroxide. That is, a soluble salt of Si or an aqueous solution thereof is added to a suspension in which iron oxyhydroxide is dispersed in water, mixed uniformly, and then the pH is adjusted to the alkali side to coat the iron oxyhydroxide surface. To wear. For pH adjustment, an alkali hydroxide such as NaOH or KOH is used. The iron oxyhydroxide coated with the soluble salt of Si is filtered, washed, and pulverized to form a fine powder. Subsequent steps are performed according to a conventional method.
C. to form hematite (α-Fe 2 O 3 ), and the deposited soluble salt of Si
It is fixed on the surface layer of Fe 2 O 3 particles. Thereafter, it is reduced with H 2 or the like to obtain Fe 3 O 4 , which is further gradually oxidized to γ-Fe
2 O 3 is obtained. Even in such a multi-step heat treatment process, sintering is effectively prevented.

【００１４】本発明の酸化鉄系磁性粉末は、Ｓｉの他に
ＹやＳｍ等の希土類元素や、Ａｌ、ＳｉあるいはＺｒ等
の副次的な形状保持剤を含有していてもよい。The iron oxide-based magnetic powder of the present invention may contain, in addition to Si, a rare earth element such as Y or Sm, or a secondary shape retainer such as Al, Si or Zr.

【００１５】本発明の酸化鉄系磁性粉末に含まれるＨ2
Ｏは、酸化鉄系磁性粉末の磁気記録層中での分散性を向
上する。水分は酸化鉄系磁性粉末の表面に吸着し、その
界面物性を制御するためと考えられる。水分量は０．１
ｗｔ％未満では分散効果が薄く、０．７ｗｔ％を超える
と磁気記録層の電気抵抗が許容範囲以上に上昇する。こ
の理由は必ずしも明らかでないが、分散性向上の結果、
個々の粒子が磁気記録層中で有機バインダにより互いに
隔絶されるため、電気伝導に寄与する電子のパスが低減
するためと推測される。酸化鉄系磁性粉末へのＨ2 Ｏの
導入は、水蒸気を含むキャリアガス、例えば湿り空気等
により、γ−Ｆｅ2 Ｏ3 状態の磁性粉末を処理すること
により施される。H 2 contained in the iron oxide-based magnetic powder of the present invention
O improves the dispersibility of the iron oxide-based magnetic powder in the magnetic recording layer. It is considered that moisture is adsorbed on the surface of the iron oxide-based magnetic powder and controls the physical properties of the interface. The water content is 0.1
If it is less than wt%, the dispersion effect is small, and if it exceeds 0.7 wt%, the electric resistance of the magnetic recording layer rises beyond an allowable range. The reason for this is not always clear, but as a result of the improved dispersibility,
It is presumed that the individual particles are isolated from each other by the organic binder in the magnetic recording layer, so that the paths of electrons contributing to electric conduction are reduced. The introduction of H 2 O into the iron oxide-based magnetic powder is performed by treating the magnetic powder in the γ-Fe 2 O 3 state with a carrier gas containing water vapor, for example, humid air.

【００１６】本発明で採用する有機バインダは、通常の
塗布型磁気記録媒体で用いられるものはいずれも使用可
能であり、ポリビニル系共重合体樹脂、ポリエステルポ
リウレタン樹脂、ポリカーボネートポリウレタン樹脂、
ニトロセルロース樹脂あるいはこれら樹脂の混合物等が
例示される。これら有機バインダ中に必要に応じて潤滑
剤、研磨剤、帯電防止剤等の各種添加剤を混合してもよ
い。これら添加剤も従来公知の材料をいずれも使用する
ことができる。また本発明で採用する非磁性支持体とし
ては、通常の塗布型磁気記録媒体で用いられるものはい
ずれも使用可能であり、ポリエチレンテレフタレート等
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、ポリ塩化ビニル等のビニル系樹脂、
ポリ塩化ビニリデン等のビニリデン樹脂、ポリカーボネ
ート、ポリアミドイミド、ポリイミド等の有機高分子が
例示される。これら非磁性支持体の磁気記録層の反対面
には、帯電防止用等のバックコート層を設けてもよい。
この他に、Ａｌ系金属、Ｔｉ系金属等の金属あるいは合
金、アルミナ等のセラミクス類、ガラス等の剛性基板を
用いてもよい。これら剛性基板の表面に、下地層として
陽極酸化被膜やＮｉ−Ｐ系めっき被膜等を形成しておい
てもよい。As the organic binder used in the present invention, any of those used in ordinary coating type magnetic recording media can be used, and a polyvinyl copolymer resin, a polyester polyurethane resin, a polycarbonate polyurethane resin,
Examples thereof include a nitrocellulose resin and a mixture of these resins. Various additives such as a lubricant, an abrasive, and an antistatic agent may be mixed into these organic binders as needed. As the additives, any conventionally known materials can be used. Further, as the non-magnetic support employed in the present invention, any of those used in ordinary coating type magnetic recording media can be used, and polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, and polyvinyl chloride. Vinyl resins such as
Examples thereof include vinylidene resins such as polyvinylidene chloride, and organic polymers such as polycarbonate, polyamideimide, and polyimide. On the surface of the non-magnetic support opposite to the magnetic recording layer, a back coat layer for antistatic or the like may be provided.
In addition, a rigid substrate such as a metal or alloy such as Al-based metal or Ti-based metal, ceramics such as alumina, or glass may be used. An anodic oxide film, a Ni-P-based plating film, or the like may be formed as a base layer on the surface of the rigid substrate.

【００１７】[0017]

【実施例】以下、本発明の具体的実施例につき、適宜比
較例を参照しつつ説明する。なお以下の各実施例および
比較例においては、酸化鉄系磁性粉末としてＣｏ変成α
−ＦｅＯＯＨを原料とするＣｏ−γ−Ｆｅ2 Ｏ3 を例に
とり説明する。EXAMPLES Hereinafter, specific examples of the present invention will be described with reference to comparative examples as appropriate. In each of the following Examples and Comparative Examples, Co-modified α was used as the iron oxide-based magnetic powder.
A description will be made by taking Co-γ-Fe 2 O 3 using —FeOOH as a raw material as an example.

【００１８】実施例１ 以下の実施例１〜３および比較例１〜２は、Ｆｅ原子に
対するＳｉ原子の含有量を変えて最適含有量を検討した
例である。酸化鉄系磁性粉末の製造 ガラス製容器中に純水３５０ｍｌおよびＣｏを含有する
α−ＦｅＯＯＨ粉末１０ｇをとり、十分に攪拌して分散
液を得た。ここにＳｉ化合物としての水ガラスの水溶液
１５ｍｌを混合し、さらに３０分間攪拌した。水ガラス
の量は、Ｆｅ原子に対するＳｉ原子の割合が０．４ａｔ
ｍ％となるように水ガラス水溶液の濃度を調製した。つ
ぎにこの分散液に１ＮのＮａＯＨ水溶液を徐々に添加し
てｐＨを９前後の弱アルカリ性とし、Ｃｏを含有するα
−ＦｅＯＯＨ粉末表面にＳｉ化合物を被着した。つぎ
に、このＳｉ化合物が被着したＣｏ含有α−ＦｅＯＯＨ
の分散液を洗浄、ろ過し、８０℃の乾燥器内で乾燥し
た。この乾燥ケーキを粉砕機により微粉化し、これを空
気中７００℃で２時間熱処理し、Ｃｏ含有α−Ｆｅ2 Ｏ
3 とした。この段階で、Ｃｏ含有α−Ｆｅ2 Ｏ3 はシリ
カにより被覆された状態となる。シリカ被覆のα−Ｆｅ
2 Ｏ3 を水素気流中４００℃で還元し、Ｃｏ−Ｆｅ3 Ｏ
4 とした後、室温近傍まで冷却し、さらに空気を徐々に
導入して徐酸化し、Ｃｏ−γ−Ｆｅ2 Ｏ3 とした。この
徐酸化工程では、Ｆｅ2+／Ｆｅ3+ イオン比が０．１５
となるように酸化量を調整した。さらに、３０℃の水バ
ブラを通した湿り空気を１．０ｌ／ｍｉｎの割合で１５
ｍｉｎ吹き込み、酸化鉄系磁性粉末を完成した。酸化鉄
系磁性粉末中の水分量は０．３ｗｔ％であった。Example 1 The following Examples 1 to 3 and Comparative Examples 1 and 2 are examples in which the optimum content was examined by changing the content of Si atoms with respect to Fe atoms. Production of Iron Oxide-Based Magnetic Powder In a glass container, 350 ml of pure water and 10 g of α-FeOOH powder containing Co were taken, and sufficiently stirred to obtain a dispersion. To this, 15 ml of an aqueous solution of water glass as a Si compound was mixed and further stirred for 30 minutes. The amount of water glass is such that the ratio of Si atoms to Fe atoms is 0.4 at.
The concentration of the water glass aqueous solution was adjusted to be m%. Next, a 1N aqueous solution of NaOH is gradually added to the dispersion to make the pH weakly alkaline at about 9, and the α
-Si compound was applied to the surface of the FeOOH powder. Next, the Co-containing α-FeOOH coated with the Si compound
Was washed, filtered and dried in a dryer at 80 ° C. The dried cake is pulverized by a pulverizer and heat-treated at 700 ° C. for 2 hours in the air to obtain Co-containing α-Fe 2 O.
It was set to 3 . At this stage, the Co-containing α-Fe 2 O 3 is coated with silica. Silica-coated α-Fe
2 O 3 is reduced at 400 ° C. in a hydrogen stream, and Co—Fe 3 O
4 and, after which cooling to around room temperature gradually oxidized further gradually introduced air was Co-γ-Fe 2 O 3 . In the slow oxidation step, the Fe 2+ / Fe 3+ ion ratio is 0.15.
The amount of oxidation was adjusted so that Further, humid air passed through a water bubbler at 30 ° C. was supplied at a rate of 1.0 l / min for 15 minutes.
min blowing to complete the iron oxide-based magnetic powder. The water content in the iron oxide-based magnetic powder was 0.3% by weight.

【００１９】磁気記録媒体の製造 上述した酸化鉄系磁性粉末により、一例として下記組成
物を混練、分散して磁性塗料を作成した。 酸化鉄系磁性粉末 １００重量部 ＶＡＧＨ １０重量部 （塩化ビニル／酢酸ビニル共重合樹脂の部分鹸化物） Ｎ−２３０４ １０重量部 （熱可塑性ポリウレタン樹脂） 研磨剤（Ａｌ2 Ｏ3 ） ３重量部 帯電防止剤（カーボン粉末） ２重量部 メチルエチルケトン １００重量部 トルエン １００重量部 シクロキサノン ５０重量部 この磁性塗料をポリエチレンテレフタレートフィルム上
に塗布、磁気配向、乾燥およびカレンダ処理して磁気記
録層を形成、実施例１のサンプルテープを作成した。 Production of Magnetic Recording Medium As an example, the following composition was kneaded and dispersed with the above-mentioned iron oxide-based magnetic powder to prepare a magnetic paint. Iron oxide magnetic powder 100 parts by weight VAGH 10 parts by weight (partially saponified vinyl chloride / vinyl acetate copolymer resin) N-2304 10 parts by weight (thermoplastic polyurethane resin) Abrasive (Al 2 O 3 ) 3 parts by weight Charge Inhibitor (carbon powder) 2 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Cycloxanone 50 parts by weight This magnetic paint is applied on a polyethylene terephthalate film, magnetically oriented, dried and calendered to form a magnetic recording layer, Example 1. A sample tape was made.

【００２０】得られた酸化鉄系磁性粉末につき、磁気特
性、比表面積および電気抵抗を測定した。磁気特性は、
飽和磁束密度σs および抗磁力Ｈｃについて、試料振動
型磁束計（東英工業（株）製）を用いて測定した。比表
面積は、Rapid Surface Area Analyzer （Micromeritic
s 社製）により測定した。電気抵抗値は、High Resista
nce Meter （ＹＨＰ社製）を用いて測定した。なお、本
発明においては、酸化鉄系磁性粉末の電気抵抗値が６．
０×１０9 Ω／□未満のものを合格と判定した。The obtained iron oxide-based magnetic powder was measured for magnetic properties, specific surface area and electric resistance. The magnetic properties are
The saturation magnetic flux density σs and the coercive force Hc were measured using a sample vibration magnetometer (manufactured by Toei Kogyo Co., Ltd.). The specific surface area is measured by Rapid Surface Area Analyzer (Micromeritic
s company). Electric resistance value is High Resista
nce Meter (YHP). In the present invention, the iron oxide-based magnetic powder has an electric resistance of 6.
Those with less than 0 × 10 9 Ω / □ were judged to be acceptable.

【００２１】実施例２ Ｆｅ原子に対するＳｉ原子の割合が０．６ａｔｍ％とな
るように水ガラス水溶液の濃度を調製した他は、Ｆｅ2+
／Ｆｅ3+ イオン比および水分量ともに実施例１に準拠
し、酸化鉄系磁性粉末およびこれを用いた磁気記録媒体
を製造した。Example 2 Except that the concentration of the aqueous solution of water glass was adjusted so that the ratio of Si atoms to Fe atoms was 0.6 atm%, Fe 2+
An iron oxide-based magnetic powder and a magnetic recording medium using the same were manufactured based on Example 1 in both the / Fe 3+ ion ratio and the water content.

【００２２】実施例３ Ｆｅ原子に対するＳｉ原子の割合が０．７ａｔｍ％とな
るように水ガラス水溶液の濃度を調製した他は、Ｆｅ2+
／Ｆｅ3+ イオン比および水分量ともに実施例１に準拠
し、酸化鉄系磁性粉末およびこれを用いた磁気記録媒体
を製造した。Example 3 Except that the concentration of the aqueous solution of water glass was adjusted so that the ratio of Si atoms to Fe atoms was 0.7 atm%, Fe 2+
An iron oxide-based magnetic powder and a magnetic recording medium using the same were manufactured based on Example 1 in both the / Fe 3+ ion ratio and the water content.

【００２３】比較例１ Ｆｅ原子に対するＳｉ原子の割合が０．３ａｔｍ％とな
るように水ガラス水溶液の濃度を調製した他は、Ｆｅ2+
／Ｆｅ3+ イオン比および水分量ともに実施例１に準拠
し、酸化鉄系磁性粉末およびこれを用いた磁気記録媒体
を製造した。COMPARATIVE EXAMPLE 1 Except that the concentration of the aqueous solution of water glass was adjusted so that the ratio of Si atoms to Fe atoms was 0.3 atm%, Fe 2+
An iron oxide-based magnetic powder and a magnetic recording medium using the same were manufactured based on Example 1 in both the / Fe 3+ ion ratio and the water content.

【００２４】比較例２ Ｆｅ原子に対するＳｉ原子の割合が１．０ａｔｍ％とな
るように水ガラス水溶液の濃度を調製した他は、Ｆｅ2+
／Ｆｅ3+ イオン比および水分量ともに実施例１に準拠
し、酸化鉄系磁性粉末およびこれを用いた磁気記録媒体
を製造した。[0024] except that the ratio of Si atoms to Comparative Example 2 Fe atoms to prepare a concentration of water glass solution so as to 1.0 atm% is, Fe 2+
An iron oxide-based magnetic powder and a magnetic recording medium using the same were manufactured based on Example 1 in both the / Fe 3+ ion ratio and the water content.

【００２５】以上、実施例１〜３および比較例１〜２の
Ｓｉ含有量を変化した酸化鉄系磁性粉末の測定結果を
〔表１〕にまとめて示す。〔表１〕では、Ｓｉ含有量の
少ない酸化鉄系磁性粉末順に配列して示した。The measurement results of the iron oxide-based magnetic powders of Examples 1 to 3 and Comparative Examples 1 and 2 having different Si contents are summarized in Table 1. In Table 1, the iron oxide-based magnetic powders having the lower Si content are arranged in order.

【００２６】[0026]

【表１】 [Table 1]

【００２７】〔表１〕から明らかなように、Ｆｅ原子に
対するＳｉ原子の量が０．７ａｔｍ％を超えると、電気
抵抗値は規格以上に増大することが判る。またこの値が
０．４ａｔｍ％未満のものは電気抵抗値は規格内である
が、磁性粒子の形状保持効果が薄らぐ結果、針状性が劣
化し、抗磁力が低下することが判明した。また電気抵抗
値が規格内の酸化鉄系磁性粉末により製造した磁気記録
媒体は、いずれも表面電気抵抗値や磁気特性、電磁変換
特性を満足するものであった。As is clear from Table 1, when the amount of Si atoms with respect to Fe atoms exceeds 0.7 atm%, the electric resistance increases more than the standard. When the value is less than 0.4 atm%, the electrical resistance value is within the standard, but as a result, the effect of retaining the shape of the magnetic particles is weakened, so that the needle-like property is deteriorated and the coercive force is reduced. Further, the magnetic recording media manufactured from the iron oxide-based magnetic powder having an electric resistance value within the standard all satisfied the surface electric resistance value, the magnetic characteristics, and the electromagnetic conversion characteristics.

【００２８】以下の実施例４および比較例３は、Ｆｅ2+
／Ｆｅ3+ イオン比を変えてその最適比を検討した例で
ある。In Example 4 and Comparative Example 3 below, Fe 2+
This is an example in which the optimum ratio was examined by changing the / Fe 3+ ion ratio.

【００２９】実施例４ 本実施例は、Ｆｅ2+／Ｆｅ3+ イオン比が０．２１とな
るように還元・徐酸化条件を設定した他は、前実施例３
に準じて酸化鉄系磁性粉末および磁気記録媒体を製造し
た例である。すなわち、Ｆｅ原子に対するＳｉ原子の量
が０．７ａｔｍ％、水分量を０．３０％として酸化鉄系
磁性粉末および磁気記録媒体を製造した。Embodiment 4 This embodiment is similar to the previous embodiment 3 except that the conditions for reduction and gradual oxidation were set so that the Fe 2+ / Fe 3+ ion ratio was 0.21.
This is an example in which an iron oxide-based magnetic powder and a magnetic recording medium are manufactured according to the method described in Example 1. That is, an iron oxide-based magnetic powder and a magnetic recording medium were manufactured with the amount of Si atoms to Fe atoms being 0.7 atm% and the amount of water being 0.30%.

【００３０】比較例３ Ｆｅ2+／Ｆｅ3+ イオン比が０．１０となるように還元
・徐酸化条件を設定した他は、前実施例４に準じて酸化
鉄系磁性粉末およびこれを用いた磁気記録媒体を製造し
た。Comparative Example 3 An iron oxide-based magnetic powder was prepared in the same manner as in Example 4 except that the conditions for reduction and gradual oxidation were set so that the Fe 2+ / Fe 3+ ion ratio was 0.10. Was manufactured.

【００３１】以上、Ｆｅ2+／Ｆｅ3+ イオン比を変えた
実施例４および比較例３と、先述した実施例３の酸化鉄
系磁性粉末の測定結果を〔表２〕にまとめて示す。なお
〔表２〕ではＦｅ2+／Ｆｅ3+ イオン比が小さい順に配
列して示した。The measurement results of the iron oxide-based magnetic powders of Example 4 and Comparative Example 3 in which the Fe 2+ / Fe 3+ ion ratio was changed and those of Example 3 described above are summarized in Table 2. In Table 2, the ratios of Fe 2+ / Fe 3+ ions are arranged in ascending order.

【００３２】[0032]

【表２】 [Table 2]

【００３３】〔表２〕から明らかなように、Ｆｅ2+／Ｆ
ｅ3+ イオン比が０．１２未満であると、酸化鉄系磁性
粉末の電気抵抗値が規格以上に増大することが判る。ま
た電気抵抗値が規格内の酸化鉄系磁性粉末により製造し
た磁気記録媒体は、いずれも表面電気抵抗値や磁気特
性、電磁変換特性を満足するものであった。As is apparent from Table 2, Fe 2+ / F
It is understood that when the e 3+ ion ratio is less than 0.12, the electric resistance value of the iron oxide-based magnetic powder increases more than the standard. Further, the magnetic recording media manufactured from the iron oxide-based magnetic powder having an electric resistance value within the standard all satisfied the surface electric resistance value, the magnetic characteristics, and the electromagnetic conversion characteristics.

【００３４】以下の実施例５〜６および比較例４は、水
分量を変えてその最適比を検討した例である。The following Examples 5 to 6 and Comparative Example 4 are examples in which the optimum ratio was examined by changing the water content.

【００３５】実施例５ 本実施例は、水分量を０．２０ｗｔ％に設定した以外
は、前実施例４と同様に酸化鉄系磁性粉末および磁気記
録媒体を製造した例である。すなわち、Ｆｅ原子に対す
るＳｉ原子の量を０．７ａｔｍ％、Ｆｅ2+／Ｆｅ3+ イ
オン比を０．２１として酸化鉄系磁性粉末および磁気記
録媒体を製造した。Example 5 In this example, an iron oxide-based magnetic powder and a magnetic recording medium were manufactured in the same manner as in Example 4 except that the water content was set to 0.20 wt%. That is, an iron oxide-based magnetic powder and a magnetic recording medium were manufactured with the amount of Si atoms to Fe atoms being 0.7 atm% and the Fe 2+ / Fe 3+ ion ratio being 0.21.

【００３６】実施例６ 本実施例は、水分量を０．７０ｗｔ％に設定した以外
は、前実施例５と同様に酸化鉄系磁性粉末および磁気記
録媒体を製造した例である。Example 6 This example is an example in which an iron oxide-based magnetic powder and a magnetic recording medium were manufactured in the same manner as in Example 5 except that the water content was set to 0.70 wt%.

【００３７】比較例４ 本実施例は、水分量を１．００ｗｔ％に設定した以外
は、前実施例５と同様に酸化鉄系磁性粉末および磁気記
録媒体を製造した例である。Comparative Example 4 In this example, an iron oxide-based magnetic powder and a magnetic recording medium were manufactured in the same manner as in Example 5 except that the water content was set to 1.00 wt%.

【００３８】以上の実施例５〜６および比較例４、なら
びに先述した実施例４の酸化鉄系磁性粉末の測定結果を
〔表３〕にまとめて示す。なお〔表３〕では、水分量の
少ない順に配列して示した。The measurement results of the iron oxide-based magnetic powders of Examples 5 to 6, Comparative Example 4, and Example 4 described above are summarized in Table 3. In addition, in [Table 3], it arrange | positioned and shown in order of the small water content.

【００３９】[0039]

【表３】 [Table 3]

【００４０】〔表３〕から明らかなように、水分量が
０．７０ｗｔ％を超えると、電気抵抗値が規格以上に増
大することが判る。また、〔表３〕には示さないが、水
分量が０．１０ｗｔ％未満の場合には電気抵抗値は規格
以内であるものの、磁性塗料中での分散性が低下する結
果、磁気記録媒体の角型比、残留磁束密度およびノイズ
特性の低下が確認された。As is clear from Table 3, when the water content exceeds 0.70 wt%, the electric resistance increases more than the standard. Although not shown in [Table 3], when the water content is less than 0.10 wt%, although the electric resistance value is within the standard, the dispersibility in the magnetic paint is reduced, and as a result, the magnetic recording medium It was confirmed that the squareness ratio, the residual magnetic flux density and the noise characteristics were reduced.

【００４１】以上、本発明を詳細に説明したが、これら
実施例は単なる例示であって、本発明はこれら実施例に
限定されることはない。例えば酸化鉄系磁性粉末として
Ｃｏ−γ−Ｆｅ2 Ｏ3 の他に単なるγ−Ｆｅ2 Ｏ3 に適
用しても本発明の効果を得ることができる。また本発明
はビデオテープの他に、オーディオテープ、コンピュー
タ用テープ、フロッピディスク、ハードディスク等、用
途を問わず高密度磁気記録媒体に好適に適用することが
可能である。Although the present invention has been described in detail above, these embodiments are merely examples, and the present invention is not limited to these embodiments. For example, the effects of the present invention can be obtained by applying the present invention to simple γ-Fe 2 O 3 in addition to Co-γ-Fe 2 O 3 as an iron oxide-based magnetic powder. Further, the present invention can be suitably applied to a high-density magnetic recording medium, such as an audio tape, a computer tape, a floppy disk, a hard disk, etc., in addition to a video tape.

【００４２】[0042]

【発明の効果】以上の説明から明らかなように、本発明
の酸化鉄系磁性粉末によれば、微細な磁性粒子の針状性
等の形状および磁気特性を劣化することなく、電気抵抗
を低減することができる。また本発明の磁気記録媒体
は、かかる酸化鉄系磁性粉末を採用することにより、磁
束密度や磁性粉の分散性を犠牲にすることなく、電気抵
抗が低減された高密度記録に好適な磁気記録媒体を提供
することが可能となる。As is apparent from the above description, according to the iron oxide-based magnetic powder of the present invention, the electric resistance can be reduced without deteriorating the shape and magnetic properties of the fine magnetic particles such as needle-like properties. can do. In addition, the magnetic recording medium of the present invention employs such an iron oxide-based magnetic powder, and without sacrificing magnetic flux density or dispersibility of the magnetic powder, magnetic recording suitable for high-density recording with reduced electric resistance. It becomes possible to provide a medium.

Claims (3)

【特許請求の範囲】[Claims] 【請求項１】 Ｓｉ原子をＦｅ原子に対して０．４ａｔ
ｍ％以上０．７ａｔｍ％以下含有するとともに、 Ｆｅ2+／Ｆｅ3+ イオン比が０．１２以上であり、 かつＨ2 Ｏを酸化鉄系磁性粉末に対して０．１ｗｔ％以
上０．７ｗｔ％以下含有することを特徴とする酸化鉄系
磁性粉末。1. The method according to claim 1, wherein the Si atom is 0.4 at.
not less than 0.7 atm% and an Fe 2+ / Fe 3+ ion ratio of not less than 0.12, and H 2 O of not less than 0.1 wt% and not more than 0.7 wt% of the iron oxide-based magnetic powder. % Of iron oxide-based magnetic powder. 【請求項２】 前記酸化鉄系磁性粉末は、γ−Ｆｅ2 Ｏ
3 およびＣｏ変成γ−Ｆｅ2 Ｏ3 のいずれかであること
を特徴とする請求項１記載の酸化鉄系磁性粉末。2. The iron oxide-based magnetic powder comprises γ-Fe 2 O.
3. The iron oxide-based magnetic powder according to claim 1, wherein the iron oxide-based magnetic powder is any one of 3 and Co-modified γ-Fe 2 O 3 . 【請求項３】 請求項１記載の酸化鉄系磁性粉末と、有
機バインダとを主体とする磁気記録層を、非磁性支持体
上に有することを特徴とする磁気記録媒体。3. A magnetic recording medium comprising a magnetic recording layer mainly comprising the iron oxide-based magnetic powder according to claim 1 and an organic binder on a nonmagnetic support.
JP8180577A 1996-07-10 1996-07-10 Iron oxide magnetic powder and magnetic recording medium formed thereof Pending JPH1027705A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP8180577A JPH1027705A (en) 1996-07-10 1996-07-10 Iron oxide magnetic powder and magnetic recording medium formed thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP8180577A JPH1027705A (en) 1996-07-10 1996-07-10 Iron oxide magnetic powder and magnetic recording medium formed thereof

Publications (1)

Publication Number Publication Date
JPH1027705A true JPH1027705A (en) 1998-01-27

Family

ID=16085708

Family Applications (1)

Application Number Title Priority Date Filing Date
JP8180577A Pending JPH1027705A (en) 1996-07-10 1996-07-10 Iron oxide magnetic powder and magnetic recording medium formed thereof

Country Status (1)

Country Link
JP (1) JPH1027705A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015194650A1 (en) * 2014-06-18 2015-12-23 国立大学法人 東京大学 Magnetic iron oxide nanopowder and process for producing same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015194650A1 (en) * 2014-06-18 2015-12-23 国立大学法人 東京大学 Magnetic iron oxide nanopowder and process for producing same
WO2015194647A1 (en) * 2014-06-18 2015-12-23 国立大学法人 東京大学 Magnetic iron oxide nanopowder and process for producing same
CN106463224A (en) * 2014-06-18 2017-02-22 国立大学法人东京大学 Magnetic iron oxide nanopowder and process for producing same
US10099941B2 (en) 2014-06-18 2018-10-16 The University Of Tokyo Magnetic iron oxide nanopowder and process for producing the same
CN106463224B (en) * 2014-06-18 2018-11-06 国立大学法人东京大学 Ferric oxide nano magnetic powder and its manufacturing method

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