JPH0252414B2 - - Google Patents
Info
- Publication number
- JPH0252414B2 JPH0252414B2 JP56151466A JP15146681A JPH0252414B2 JP H0252414 B2 JPH0252414 B2 JP H0252414B2 JP 56151466 A JP56151466 A JP 56151466A JP 15146681 A JP15146681 A JP 15146681A JP H0252414 B2 JPH0252414 B2 JP H0252414B2
- Authority
- JP
- Japan
- Prior art keywords
- magnetic
- cobalt
- iron oxide
- powder
- magnetic powder
- 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.)
- Expired - Lifetime
Links
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 50
- 239000010941 cobalt Substances 0.000 claims description 32
- 229910017052 cobalt Inorganic materials 0.000 claims description 32
- 239000006247 magnetic powder Substances 0.000 claims description 32
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 29
- 239000002245 particle Substances 0.000 claims description 13
- 239000010410 layer Substances 0.000 claims description 11
- 230000004907 flux Effects 0.000 claims description 9
- 239000013078 crystal Substances 0.000 claims description 8
- 239000002344 surface layer Substances 0.000 claims description 3
- 230000005415 magnetization Effects 0.000 description 13
- 239000000843 powder Substances 0.000 description 8
- 229910001566 austenite Inorganic materials 0.000 description 7
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 239000003973 paint Substances 0.000 description 6
- 239000007858 starting material Substances 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 4
- 150000001868 cobalt Chemical class 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 229920005989 resin Polymers 0.000 description 3
- 239000011347 resin Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 description 2
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- 229920002554 vinyl polymer Polymers 0.000 description 2
- SPBDXSGPUHCETR-JFUDTMANSA-N 8883yp2r6d Chemical compound O1[C@@H](C)[C@H](O)[C@@H](OC)C[C@@H]1O[C@@H]1[C@@H](OC)C[C@H](O[C@@H]2C(=C/C[C@@H]3C[C@@H](C[C@@]4(O[C@@H]([C@@H](C)CC4)C(C)C)O3)OC(=O)[C@@H]3C=C(C)[C@@H](O)[C@H]4OC\C([C@@]34O)=C/C=C/[C@@H]2C)/C)O[C@H]1C.C1C[C@H](C)[C@@H]([C@@H](C)CC)O[C@@]21O[C@H](C\C=C(C)\[C@@H](O[C@@H]1O[C@@H](C)[C@H](O[C@@H]3O[C@@H](C)[C@H](O)[C@@H](OC)C3)[C@@H](OC)C1)[C@@H](C)\C=C\C=C/1[C@]3([C@H](C(=O)O4)C=C(C)[C@@H](O)[C@H]3OC\1)O)C[C@H]4C2 SPBDXSGPUHCETR-JFUDTMANSA-N 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 229920006311 Urethane elastomer Polymers 0.000 description 1
- 229920002433 Vinyl chloride-vinyl acetate copolymer Polymers 0.000 description 1
- 239000003082 abrasive agent Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 239000002216 antistatic agent Substances 0.000 description 1
- ULBTUVJTXULMLP-UHFFFAOYSA-N butyl octadecanoate Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCCCC ULBTUVJTXULMLP-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229940044175 cobalt sulfate Drugs 0.000 description 1
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 1
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 238000007756 gravure coating Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 239000012948 isocyanate Substances 0.000 description 1
- -1 isocyanate compound Chemical class 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000011859 microparticle Substances 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 229920005749 polyurethane resin Polymers 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 235000011121 sodium hydroxide Nutrition 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/842—Coating a support with a liquid magnetic dispersion
- G11B5/845—Coating a support with a liquid magnetic dispersion in a magnetic field
Description
この発明は磁気記録媒体に関し、その目的とす
るところは特に高密度記録に適した磁気記録媒体
を提供することにある。
一般に、磁気テープなどの磁気記録媒体は、磁
性層中の針状磁性粉末を磁気テープの長手方向に
配向させるなどして磁気特性を向上させている
が、このように針状磁性粉末を長手方向に配向さ
せたものでは長手方向の磁化を用いているため記
録密度の向上に限度があり、信号の記録密度を増
加してゆくと磁気記録媒体内の反磁界が増加して
残留磁化の減衰と回転を生じ、記録信号の検出が
困難となる。
このため、垂直磁気記録に適した特性を有する
コバルト含有酸化鉄磁性粉末を長手方向に配向し
ないで記録素子として用いるなどの試みがなされ
ており、従来から磁気デイスクなどの磁気記録媒
体においては針状で一軸異方性のコバルト含有酸
化鉄磁性粉末を無配向で磁性層中に含有させるこ
とが行なわれている。
ところが、この磁気デイスクなどの磁気記録媒
体の磁性層中に含有されているコバルト含有酸化
鉄磁性粉末は、通常粒径が0.4μ程度のもので粒径
が大きく、また配向方向は水平面内で長手方向に
配向せず無配向にしているだけで垂直方向の配向
は全く考慮されていないため、垂直磁化が充分に
良好でなく、記録波長1μ以下の短波長記録が良
好に行なえないなどの難点があり、高密度記録が
充分に行なえない。
この発明者らはかかる事情に鑑み種々検討を行
なつた結果、磁性層中に含有する磁性粉末とし
て、酸化鉄磁性粉末を核晶とし、この核晶上にコ
バルトを主体的に含ませた表面層を有する一軸異
方性でかつ粒径が0.3μ以下の針状磁性粉末を使用
し、この磁性粉末を含有する磁性層の垂直方向の
残留磁束密度が1000ガウス以上となるように配向
させると、磁性層の垂直磁化が充分に良好になつ
て高密度範囲における記録特性が充分に向上し、
記録波長が1μ以下の短波長記録を充分に行なえ
る磁気記録媒体が得られることを見い出し、この
発明をなすに至つた。
この発明において使用されるコバルト含有酸化
鉄粉末は、酸化鉄粉末を核晶とし、この核晶上に
コバルトを主体的に含ませた表面層を有する一軸
異方性で粒径が0.3μ以下の針状の磁性粉末である
ことが好ましく、粒径が0.3μより大きくなると磁
気テープの表面平滑性が悪くなりこの種の高密度
記録用磁性材料としては好ましくない。またコバ
ルトの含有量は磁性粉末全量に対して２〜15重量
％の範囲内で含有させるのが好ましい。このよう
なコバルト含有酸化鉄磁性粉末は、コバルト原子
を均一に固溶しているものに比べて、加熱、加圧
減磁が少なく、加熱、加圧減磁を起こし易い0.3μ
以下の微小粒径のものを使用する本発明において
は、特に好適である。
このような酸化鉄磁性粉末を核晶とし、この核
晶上にコバルトを主体的に含ませた表面層を有す
る一軸異方性で粒径が0.3μ以下の針状のコバルト
含有酸化鉄磁性粉末は、結合剤等とともにロール
コーターまたはグラビア塗布など任意の手段で基
体上に塗布し、棒磁石、馬てい形磁石などを使用
して基体に対し垂直方向の磁界により垂直方向に
配向しながら乾燥し、得られる磁性層の垂直方向
の残留磁束密度を1000ガウス以上にするのが好ま
しく、垂直方向の残留磁束密度が1000ガウスより
小さいと磁気テープの記録再生において短波長で
の出力が充分ではない。
このように、前記のコバルト含有酸化鉄磁性粉
末を結合剤樹脂、有機溶剤およびその他の必要成
分とともに垂直方向に配向するように基体上に塗
布、乾燥して磁性層を形成し、磁性層の垂直方向
の残留磁束密度を1000ガウス以上にすると、垂直
磁化が充分に良好になつて高密度範囲における記
録特性が向上し、記録波長が1μ以下の短波長記
録が充分に行なえる磁気記録媒体が得られる。
ここに用いる結合剤樹脂としては、塩化ビニル
−酢酸ビニル系共重合体、ポリビニルブチラー
ル、ポリウレタン系樹脂、ニトロセルロースなど
従来汎用されている結合剤樹脂が広く用いられ
る。
また、有機溶剤としては、トルエン、メチルイ
ソブチルケトン、メチルエチルケトン、シクロヘ
キサノン、テトラヒドロフラン、酢酸エチルなど
従来から汎用されている有機溶剤から適宜選択
し、これらを単独または二種以上混合して使用す
ればよい。
なお、磁性塗料中には通常使用されている各種
添加剤、たとえば分散剤、潤滑剤、研磨剤、帯電
防止剤などを任意に添加使用してもよい。
次に、この発明の実施例について説明する。
実施例 １
出発原料として粒径（長軸）0.15μ、軸比（長
軸／短軸）８のγ−Fe2O3を使用し、これを６
の水に分散させた後、硫酸コバルト258ｇと硫酸
第一鉄766ｇとを加えて混合溶解し、次いで３
の水に溶解した苛性ソーダ1014ｇを加えて混合し
た後、45℃で６時間反応させた。反応終了後、水
洗、脱水、乾燥して得られたコバルト含有酸化鉄
磁性粉末は一軸異方性の針状粉末で、コバルト含
有量は4.9重量％で、保磁力（Hc）は910エルス
テツド、飽和磁化量（σs）は77emu／ｇ、角型
（σr／σs）は0.49であつた。
このようにして得られたコバルト含有酸化鉄磁
性粉末を使用し、
Co含有γ−F2O3粉末 750重量部
VAGH（米国U.C.C社製、塩化ビニル−酢酸ビ
ニル−ビニルアルコール共重合体） 125〃
パンデツクスＴ−5250（大日本インキ社製、ウ
レタンエラストマー） 100〃
コロネートＬ（日本ポリウレタン工業社製、三
官能性低分子量イソシアネート化合物）
25重量部
ステアリン酸−ｎ−ブチル 15〃
メチルイソブチルケトン 600〃
トルエン 600〃
の組成からなる組成物をボールミル中で３日間混
合分散して磁性塗料を調製した。この磁性塗料を
厚さ12μのポリエステルベースフイルム上にグラ
ビアロールで塗布し、磁界を印加して一時的に塗
料を滞留させることによつて塗膜を平滑化した
後、対向た異極磁場中を走行させて垂直配向処理
を施こし、乾燥して乾燥厚が3μの磁性層を形成
した。次いで形成された磁性層の表面処理を行な
つた後、所定の巾に裁断して磁気テープをつくつ
た。
実施例 ２
実施例１において、出発原料として粒径（長
軸）0.2μ、軸比（長軸／短軸）８のγ−Fe2O3を
使用した以外は実施例１と同様にしてコバルト含
有量は4.9重量％、保磁力（Hc）900エルステツ
ド、飽和磁化量（σs）76.8emu／ｇ、角型（σr／
σs）0.49の針状で一軸異方性のコバルト含有酸化
鉄磁性粉末を得、さらにこのコバルト含有酸化鉄
磁性粉末を使用して実施例１と同様にして磁気テ
ープをつくつた。
実施例 ３
実施例１において、出発原料として粒径（長
軸）0.3μ、軸比（長軸／短軸）８のγ−Fe2O3粉
末を使用した以外は実施例１と同様にしてコバル
ト含有量4.9重量％、保磁力（Hc）950エルステ
ツド、飽和磁化量（σs）77.5emu／ｇ、角型
（σr／σs）0.49の針状で一軸異方性のコバルト含
有酸化鉄磁性粉末を得、さらにこのコバルト含有
酸化鉄磁性粉末を使用して実施例１と同様にして
磁気テープをつくつた。
実施例 ４
実施例１において、出発原料として粒径（長
軸）0.15μ、軸比（長軸／短軸）５のγ−Fe2O3
を使用した以外は実施例１と同様にしてコバルト
含有量4.9重量％、保磁力（Hc）910エルステツ
ド、飽和磁化量（σs）77.5emu／ｇ、角型（σr／
σs）0.49の針状で一軸異方性のコバルト含有酸化
鉄磁性粉末を得、さらにこのコバルト含有酸化鉄
磁性粉末を使用して実施例１と同様にして磁気テ
ープをつくつた。
実施例 ５
実施例１において、出発原料として粒径（長
軸）0.15μ、軸比（長軸／短軸）3.5のγ−Fe2O3
粉末を使用した以外は実施例１と同様にしてコバ
ルト含有量4.9重量％、保磁力（Hc）850エルス
テツド、飽和磁化量（σs）77.3emu／ｇ、角型
（σr／σs）0.49の針状で一軸異方性のコバルト含
有酸化鉄磁性粉末を得、さらにこのコバルト含有
酸化鉄磁性粉末を使用して実施例１と同様にして
磁気テープをつくつた。
比較例 １
実施例１において出発原料として粒径（長軸）
0.4μ、軸比（長軸／短軸）８のγ−Fe2O3を使用
した以外は実施例１と同様にしてコバルト含有酸
化鉄磁性粉末を製造した。得られたコバルト含有
酸化鉄磁性粉末は一軸異方性の針状の粉末で、コ
バルト含有量は4.9重量％で、保磁力（Hc）は
930エルステツド、飽和磁化量（σs）は
77.1emu／ｇ、角型（σr／σs）は0.50であつた。
このようにして得られたコバルト含有酸化鉄磁
性粉末を、実施例１における磁性塗料のCo含有
γ−Fe2O3粉末に代えて同量使用し、実施例１に
おける磁性粉末の無配向処理に代えてグラビアロ
ールで塗布した後、塗膜にプラスチツクシートを
接触させて表面を平滑化した以外は実施例１と同
様にして磁気テープをつくつた。
比較例 ２
実施例１で得られたと同じコバルト含有酸化鉄
磁性粉末を使用し、実施例１における磁性粉末の
配向処理に代えて、ベースフイルム面に対し、表
裏両面に配置された一対の棒磁石によつてベース
フイルムの長手方向に3000ガウスの対向磁場を加
えて配向処理を施こした以外は実施例１と同様に
して磁気テープをつくつた。
各実施例および各比較例で得られた磁気テープ
について、長手方向の保磁力（Hc）、残留磁束密
度（Br）、最大磁束密度（Bs）および角型
（Br／Bs）と垂直方向の保磁力（Hc）、残留磁束
密度（Br）および角型（Br／Bs）を測定し、配
向比（垂直方向の角型／長手方向の角型）を測定
した。また各種記録波長における最大出力レベル
（M.O.L）を測定した。
下表はその結果である。
The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium particularly suitable for high-density recording. Generally, the magnetic properties of magnetic recording media such as magnetic tape are improved by orienting the acicular magnetic powder in the magnetic layer in the longitudinal direction of the magnetic tape. Since those oriented in the magnetic recording medium use magnetization in the longitudinal direction, there is a limit to the improvement in recording density.As the signal recording density increases, the demagnetizing field within the magnetic recording medium increases, resulting in attenuation of residual magnetization. Rotation occurs, making it difficult to detect the recorded signal. For this reason, attempts have been made to use cobalt-containing iron oxide magnetic powder, which has characteristics suitable for perpendicular magnetic recording, as a recording element without being oriented in the longitudinal direction. In recent years, uniaxially anisotropic cobalt-containing iron oxide magnetic powder has been incorporated into the magnetic layer without orientation. However, the cobalt-containing iron oxide magnetic powder contained in the magnetic layer of magnetic recording media such as magnetic disks usually has a large particle size of about 0.4μ, and the orientation direction is longitudinal in the horizontal plane. Since the perpendicular magnetization is not taken into account at all, and the perpendicular magnetization is not sufficiently good, short wavelength recording of less than 1 μm cannot be performed well. Yes, high-density recording cannot be performed sufficiently. The inventors conducted various studies in view of the above circumstances, and found that the magnetic powder contained in the magnetic layer was made of iron oxide magnetic powder as a core crystal, and a surface containing cobalt primarily on the core crystal. When a uniaxially anisotropic acicular magnetic powder with a particle size of 0.3 μ or less is used and oriented so that the residual magnetic flux density in the perpendicular direction of the magnetic layer containing this magnetic powder is 1000 Gauss or more, , the perpendicular magnetization of the magnetic layer becomes sufficiently good, and the recording characteristics in the high density range are sufficiently improved.
It was discovered that a magnetic recording medium capable of sufficiently performing short wavelength recording with a recording wavelength of 1 μm or less can be obtained, and the present invention was completed. The cobalt-containing iron oxide powder used in this invention is uniaxially anisotropic and has a particle size of 0.3μ or less, with iron oxide powder as a core crystal, and a surface layer containing mainly cobalt on the core crystal. Acicular magnetic powder is preferable; if the particle size is larger than 0.3 μm, the surface smoothness of the magnetic tape deteriorates, which is not preferable for this type of magnetic material for high-density recording. Further, the content of cobalt is preferably within the range of 2 to 15% by weight based on the total amount of magnetic powder. This kind of cobalt-containing iron oxide magnetic powder has less demagnetization due to heating and pressure, compared to those in which cobalt atoms are uniformly dissolved in solid solution.
In the present invention, particles having the following microparticle diameters are particularly suitable. Uniaxially anisotropic, acicular cobalt-containing iron oxide magnetic powder with a particle size of 0.3μ or less, which uses such iron oxide magnetic powder as a core crystal and has a surface layer containing mainly cobalt on the core crystal. is applied onto a substrate by any means such as a roll coater or gravure coating along with a binder, etc., and dried while being orientated in a vertical direction by a magnetic field perpendicular to the substrate using a bar magnet, horse-shaped magnet, etc. It is preferable that the residual magnetic flux density in the perpendicular direction of the obtained magnetic layer is 1000 Gauss or more, and if the residual magnetic flux density in the vertical direction is smaller than 1000 Gauss, the output at short wavelengths will not be sufficient in recording and reproducing magnetic tape. In this way, the above-mentioned cobalt-containing iron oxide magnetic powder is coated on a substrate so as to be vertically oriented together with a binder resin, an organic solvent, and other necessary components, and dried to form a magnetic layer. When the residual magnetic flux density in the direction is set to 1000 Gauss or more, the perpendicular magnetization becomes sufficiently good, the recording characteristics in the high density range improve, and a magnetic recording medium that can perform short wavelength recording with a recording wavelength of 1 μ or less can be obtained. It will be done. As the binder resin used here, conventionally widely used binder resins such as vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyurethane resin, and nitrocellulose are widely used. Further, the organic solvent may be appropriately selected from conventionally widely used organic solvents such as toluene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, and ethyl acetate, and these may be used alone or in a mixture of two or more. Incidentally, various commonly used additives such as dispersants, lubricants, abrasives, antistatic agents, etc., may be optionally added to the magnetic paint. Next, embodiments of the invention will be described. Example 1 γ-Fe 2 O 3 with a particle size (long axis) of 0.15μ and an axial ratio (long axis/short axis) of 8 was used as a starting material, and this was
After dispersing in water, 258 g of cobalt sulfate and 766 g of ferrous sulfate were added and mixed and dissolved.
After adding and mixing 1014 g of caustic soda dissolved in water, the mixture was reacted at 45°C for 6 hours. After completion of the reaction, the cobalt-containing iron oxide magnetic powder obtained by washing with water, dehydration, and drying is a uniaxially anisotropic needle-shaped powder with a cobalt content of 4.9% by weight, a coercive force (Hc) of 910 oersted, and a saturated The magnetization (σs) was 77 emu/g, and the square shape (σr/σs) was 0.49. Using the thus obtained cobalt-containing iron oxide magnetic powder, 750 parts by weight of Co-containing γ-F 2 O 3 powder VAGH (manufactured by UCC, USA, vinyl chloride-vinyl acetate-vinyl alcohol copolymer) 125〃 Pandex T-5250 (manufactured by Dainippon Ink Co., Ltd., urethane elastomer) 100〃 Coronate L (manufactured by Nippon Polyurethane Industries Co., Ltd., trifunctional low molecular weight isocyanate compound)
A magnetic paint was prepared by mixing and dispersing a composition consisting of 25 parts by weight of n-butyl stearate, 15 parts methyl isobutyl ketone, 600 parts, and 600 parts toluene in a ball mill for 3 days. This magnetic paint is applied onto a 12μ thick polyester base film using a gravure roll, the paint film is smoothed by applying a magnetic field and temporarily retaining the paint, and then exposed to an opposite polar magnetic field. It was run, subjected to vertical alignment treatment, and dried to form a magnetic layer with a dry thickness of 3 μm. Next, the formed magnetic layer was subjected to surface treatment, and then cut to a predetermined width to produce a magnetic tape. Example 2 Cobalt was produced in the same manner as in Example 1, except that γ-Fe 2 O 3 with a particle size (major axis) of 0.2μ and an axial ratio (major axis/minor axis) of 8 was used as the starting material. Content is 4.9% by weight, coercive force (Hc) 900 oersted, saturation magnetization (σs) 76.8emu/g, square shape (σr/
Acicular, uniaxially anisotropic cobalt-containing iron oxide magnetic powder having an σs) of 0.49 was obtained, and a magnetic tape was produced in the same manner as in Example 1 using this cobalt-containing iron oxide magnetic powder. Example 3 The same procedure as in Example 1 was carried out except that γ-Fe 2 O 3 powder with a particle size (long axis) of 0.3 μ and an axial ratio (long axis/short axis) of 8 was used as the starting material. Acicular and uniaxially anisotropic cobalt-containing iron oxide magnetic powder with a cobalt content of 4.9% by weight, a coercive force (Hc) of 950 oersted, a saturation magnetization (σs) of 77.5emu/g, and a square shape (σr/σs) of 0.49. A magnetic tape was prepared in the same manner as in Example 1 using this cobalt-containing iron oxide magnetic powder. Example 4 In Example 1, the starting material was γ-Fe 2 O 3 with a particle size (long axis) of 0.15μ and an axial ratio (long axis/short axis) of 5.
Cobalt content 4.9% by weight, coercive force (Hc) 910 oersted, saturation magnetization (σs) 77.5emu/g, square shape (σr/
Acicular, uniaxially anisotropic cobalt-containing iron oxide magnetic powder having an σs) of 0.49 was obtained, and a magnetic tape was produced in the same manner as in Example 1 using this cobalt-containing iron oxide magnetic powder. Example 5 In Example 1, the starting material was γ-Fe 2 O 3 with a particle size (long axis) of 0.15 μ and an axial ratio (long axis/short axis) of 3.5.
A needle-like material with a cobalt content of 4.9% by weight, a coercive force (Hc) of 850 oersted, a saturation magnetization (σs) of 77.3emu/g, and a square shape (σr/σs) of 0.49 was prepared in the same manner as in Example 1 except that powder was used. A uniaxially anisotropic cobalt-containing iron oxide magnetic powder was obtained, and a magnetic tape was produced in the same manner as in Example 1 using this cobalt-containing iron oxide magnetic powder. Comparative Example 1 Particle size (long axis) as the starting material in Example 1
A cobalt-containing iron oxide magnetic powder was produced in the same manner as in Example 1 except that γ-Fe 2 O 3 having a diameter of 0.4μ and an axial ratio (major axis/minor axis) of 8 was used. The obtained cobalt-containing iron oxide magnetic powder is a uniaxially anisotropic needle-shaped powder with a cobalt content of 4.9% by weight and a coercive force (Hc) of
930 oersted, saturation magnetization (σs) is
The squareness (σr/σs) was 77.1emu/g and 0.50. The thus obtained cobalt-containing iron oxide magnetic powder was used in the same amount in place of the Co-containing γ-Fe 2 O 3 powder in the magnetic paint in Example 1, and was used in the non-oriented treatment of the magnetic powder in Example 1. A magnetic tape was prepared in the same manner as in Example 1, except that after coating with a gravure roll, the surface was smoothed by bringing a plastic sheet into contact with the coating film. Comparative Example 2 The same cobalt-containing iron oxide magnetic powder as obtained in Example 1 was used, and instead of the orientation treatment of the magnetic powder in Example 1, a pair of bar magnets were placed on both the front and back sides of the base film surface. A magnetic tape was produced in the same manner as in Example 1, except that an opposing magnetic field of 3,000 Gauss was applied in the longitudinal direction of the base film for orientation treatment. The longitudinal coercive force (Hc), residual magnetic flux density (Br), maximum magnetic flux density (Bs), rectangular shape (Br/Bs), and perpendicular coercive force for the magnetic tapes obtained in each example and each comparative example. Magnetic force (Hc), residual magnetic flux density (Br), and squareness (Br/Bs) were measured, and the orientation ratio (squareness in the vertical direction/squareness in the longitudinal direction) was measured. We also measured the maximum output level (MOL) at various recording wavelengths. The table below shows the results.
【表】【table】
【表】
上表から明らかなように、この発明で得られた
磁気テープ（実施例１〜５）は従来の磁気テープ
（比較例１〜２）に比べて、いずれも垂直方向の
保磁力、残留磁束密度および角型が大きくて配向
比も大きく、1μ以下の短波長での最大出力レベ
ルが大きい。このことからこの発明によつて得ら
れる磁気記録媒体は垂直磁化が良好で高密度記録
に優れていることがわかる。[Table] As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 to 5) have higher coercive force in the perpendicular direction, It has a large residual magnetic flux density, a large square shape, a large orientation ratio, and a large maximum output level at short wavelengths of 1μ or less. This shows that the magnetic recording medium obtained by the present invention has good perpendicular magnetization and is excellent in high-density recording.
Claims (1)
バルトを主体的に含ませた表面層を有する一軸異
方性で粒径が0.3μ以下の針状磁性粉末を磁性層中
に含有させ、垂直方向の残留磁束密度を1000ガウ
ス以上となるように配向したことを特徴とする磁
気記録媒体。1 Iron oxide magnetic powder is used as a core crystal, and a magnetic layer contains uniaxially anisotropic acicular magnetic powder with a particle size of 0.3μ or less, which has a surface layer containing mainly cobalt on the core crystal. , a magnetic recording medium characterized by being oriented so that the residual magnetic flux density in the vertical direction is 1000 Gauss or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56151466A JPS5852803A (en) | 1981-09-24 | 1981-09-24 | Magnetic recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56151466A JPS5852803A (en) | 1981-09-24 | 1981-09-24 | Magnetic recording medium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5852803A JPS5852803A (en) | 1983-03-29 |
| JPH0252414B2 true JPH0252414B2 (en) | 1990-11-13 |
Family
ID=15519143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56151466A Granted JPS5852803A (en) | 1981-09-24 | 1981-09-24 | Magnetic recording medium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5852803A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0618061B2 (en) * | 1983-03-14 | 1994-03-09 | 日立マクセル株式会社 | Magnetic recording medium |
| JPS633404U (en) * | 1986-06-25 | 1988-01-11 | ||
| US4944985A (en) * | 1988-04-11 | 1990-07-31 | Leach & Garner | Method for electroless plating of ultrafine or colloidal particles and products produced thereby |
| JPH02204001A (en) * | 1989-02-02 | 1990-08-14 | Meinan Mach Works Inc | Plywood and manufacture thereof |
-
1981
- 1981-09-24 JP JP56151466A patent/JPS5852803A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5852803A (en) | 1983-03-29 |
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