JP4352270B2 - Hematite particle powder for nonmagnetic underlayer of magnetic recording medium and magnetic recording medium - Google Patents
Hematite particle powder for nonmagnetic underlayer of magnetic recording medium and magnetic recording medium Download PDFInfo
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本発明は、充填性に優れ、しかも、カレンダー処理による表面平滑性の向上が期待できる磁気記録媒体の非磁性下地層用非磁性粉末として好適なヘマタイト粒子粉末を提供する。 The present invention provides a hematite particle powder suitable as a nonmagnetic powder for a nonmagnetic underlayer of a magnetic recording medium, which is excellent in filling properties and can be expected to improve surface smoothness by calendering.
近年、ビデオ用、オーディオ用磁気記録再生用機器の長時間記録化、小型軽量化が進むにつれて、磁気テープ、磁気ディスク等の磁気記録媒体に対する高性能化、即ち、高密度記録化、高出力特性、殊に周波数特性の向上、低ノイズ化の要求が強まっている。 In recent years, as video recording and audio magnetic recording / reproducing devices have been recorded for a long time and reduced in size and weight, the performance of magnetic recording media such as magnetic tapes and magnetic disks has been improved, that is, higher recording density and higher output characteristics. In particular, there is an increasing demand for improved frequency characteristics and low noise.
殊に、近時におけるビデオテープの高画像高画質化に対する要求は益々強まっており、従来のビデオテープに比べ、記録されるキャリアー信号の周波数が短波長領域に移行しており、その結果、磁気テープの表面からの磁化深度が著しく浅くなっている。 In particular, the recent demand for higher image quality on video tapes has been increasing, and compared to conventional video tapes, the frequency of the carrier signal to be recorded has shifted to the short wavelength region. The magnetization depth from the surface of the tape is remarkably shallow.
短波長信号に対して、磁気記録媒体の高出力特性、殊に、S/N比を向上させるためには、磁気記録層の薄層化が強く要求されている。磁気記録層を薄層化するためには、磁気記録層を平滑にし、且つ、厚みむらを少なくする必要がある。そのためには、ベースフィルムの表面もまた平滑でなければならない。 In order to improve the high output characteristics of a magnetic recording medium, particularly the S / N ratio, with respect to a short wavelength signal, it is strongly required to reduce the thickness of the magnetic recording layer. In order to reduce the thickness of the magnetic recording layer, it is necessary to smooth the magnetic recording layer and reduce the thickness unevenness. For this purpose, the surface of the base film must also be smooth.
一般に磁気記録媒体は、ベースフィルム等の非磁性支持体上に磁性粒子粉末と結合剤樹脂を含む磁気記録層を形成し、カレンダーをかけて表面平滑化処理を行うことにより磁気記録層の平滑化を行っている。 In general, a magnetic recording medium is formed by forming a magnetic recording layer containing magnetic particle powder and a binder resin on a nonmagnetic support such as a base film, and smoothing the magnetic recording layer by applying a calendar to smooth the surface. It is carried out.
近年、磁気記録層の薄層化が一層進む中で、ベースフィルム等の非磁性支持体上に針状へマタイト粒子粉末等の非磁性粒子粉末を結合剤樹脂中に分散させてなる下地層(以下、「非磁性下地層」という。)を一層設けることにより、磁気記録層の表面性の悪化や電磁変換特性を劣化させる等の問題を解決することが提案され、実用化されている(特公平6−93297号公報、特開昭62−159338号公報、特開昭63−187418号公報、特開平4−167225号公報、特開平4−325915公報、特開平5−73882号公報、特開平5−182177号公報)。 In recent years, as the magnetic recording layer is further thinned, an underlayer (non-magnetic particle powder such as matite particle powder dispersed in a binder resin on a nonmagnetic support such as a base film is dispersed (in a binder resin). Hereinafter, it has been proposed and put into practical use to solve problems such as deterioration of the surface properties of the magnetic recording layer and electromagnetic conversion characteristics by providing a single layer of “non-magnetic underlayer”. Japanese Patent Publication No. 6-93297, Japanese Patent Application Laid-Open No. 62-159338, Japanese Patent Application Laid-Open No. 63-187418, Japanese Patent Application Laid-Open No. 4-167225, Japanese Patent Application Laid-Open No. 4-325915, Japanese Patent Application Laid-Open No. No. 5 -182177).
前記非磁性下地層を有する磁気記録媒体の場合には、非磁性支持体上に非磁性粉末と結合剤樹脂とを含有する非磁性下地層及び磁性粒子粉末と結合剤樹脂とを含有する磁気記録層を形成し、次いで、カレンダー処理を行い非磁性支持体の凹凸を非磁性下地層が吸収することによって、磁気記録層の表面平滑化を図っている。例えば、特開平5−12650号公報には、「……非磁性の緩衝層を設けることにより六方晶系フェライト磁性粉体を含む層が表面平滑化処理する際に直下の非磁性層がバッファー層として押しつぶされる。これにより下層(非磁性層のこと?)が吸収層として作用し、上層の六方晶系フェライト板状磁性粉を含む磁気記録層が平滑化されることになる。」と記載されている。 In the case of the magnetic recording medium having the nonmagnetic underlayer, the nonmagnetic underlayer containing the nonmagnetic powder and the binder resin on the nonmagnetic support and the magnetic recording containing the magnetic particle powder and the binder resin. A layer is formed, and then a calendering process is performed so that the nonmagnetic underlayer absorbs the irregularities of the nonmagnetic support, thereby smoothing the surface of the magnetic recording layer. For example, in Japanese Patent Laid-Open No. 5-12650, “... a nonmagnetic buffer layer is provided with a nonmagnetic buffer layer. As a result, the lower layer (which is a nonmagnetic layer?) Acts as an absorbing layer, and the magnetic recording layer containing the upper hexagonal ferrite plate-like magnetic powder is smoothed. ing.
非磁性下地層の表面平滑性を改善するためには、分散性及び充填性が優れていると共にカレンダー処理による表面平滑性の向上が期待できるヘマタイト粒子粉末を用いることが要求されている。 In order to improve the surface smoothness of the nonmagnetic underlayer, it is required to use hematite particle powder that is excellent in dispersibility and filling properties and can be expected to improve the surface smoothness by calendering.
従来、磁気記録媒体の諸特性改善のために、非磁性下地層用非磁性粒子粉末に対して種々の試みがなされており、例えば、特許文献1(特開平6−60362号公報)にはAl化合物によって被覆されている針状ヘマタイト粒子粉末からなる非磁性粒子粉末を含有する磁気記録媒体用非磁性下地層が記載されており、特許文献2(特開平7−129947号公報)及び特許文献3(特開平8−279138号公報)には非磁性下地層用非磁性粒子粉末として粒子形状が紡錘状であるヘマタイト粒子粉末を用いた磁気記録媒体が記載されており、特許文献4(特開平10−334450号公報)には磁気記録媒体の非磁性下地層に結晶学的なa軸方向に、同一結晶面同士が3個以内で重なり接合している針状ゲータイト微粒子を用いた磁気記録媒体が記載されている。 Conventionally, various attempts have been made on nonmagnetic particle powders for nonmagnetic underlayers in order to improve various characteristics of magnetic recording media. For example, Patent Document 1 (Japanese Patent Laid-Open No. 6-60362) discloses Al. Non-magnetic underlayers for magnetic recording media containing non-magnetic particle powders consisting of acicular hematite particle powders coated with a compound are described. Patent Document 2 (Japanese Patent Laid-Open No. 7-129947) and Patent Document 3 (JP-A-8-279138) describes a magnetic recording medium using a hematite particle powder having a spindle shape as a nonmagnetic particle powder for a nonmagnetic underlayer. No. -334450) describes magnetic recording using acicular goethite fine particles in which no more than three identical crystal planes are bonded to each other in the crystallographic a-axis direction on a nonmagnetic underlayer of a magnetic recording medium. Body have been described.
表面平滑性がより優れた磁気記録媒体を得ることができる非磁性下地層用非磁性粒子粉末として好適なヘマタイト粒子粉末は現在最も要求されているところであるが、未だ得られていない。 A hematite particle powder suitable as a nonmagnetic particle powder for a nonmagnetic underlayer capable of obtaining a magnetic recording medium with better surface smoothness is currently most demanded, but has not yet been obtained.
即ち、前出特許文献1(特開平6−60362号公報)記載のヘマタイト粒子粉末は、長軸方向に方向性をもって配列した構造を有しておらず、カレンダー処理による表面平滑効果が得られにくい。 That is, the hematite particle powder described in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 6-60362) does not have a structure arranged with directionality in the major axis direction, and it is difficult to obtain a surface smoothing effect by calendering. .
前出特許文献2(特開平7−129947号公報)及び前出特許文献3(特開平8−279138号公報)記載の紡錘状ヘマタイト粒子粉末は、後述比較例に示す通り、BET比表面積値が100m2/g未満であってシクロヘキサノンの吸液量が0.6ml/g未満であるため、紡錘状ヘマタイト粒子の粒子端が閉じているものと推定され、充填性に優れるとは言い難いものである。 The spindle-shaped hematite particles described in Patent Document 2 (Japanese Patent Laid-Open No. 7-129947) and Patent Document 3 (Japanese Patent Laid-Open No. 8-279138) have a BET specific surface area value as shown in Comparative Examples described later. Since it is less than 100 m 2 / g and the liquid absorption of cyclohexanone is less than 0.6 ml / g, it is presumed that the end of the spindle-shaped hematite particles is closed, and it is difficult to say that the filling property is excellent. is there.
また、前出特許文献4(特開平10−334450号公報)記載のゲータイト粒子粉末を非磁性下地層用非磁性粉末として用いた場合には、ゲータイト粒子粉末の粒子表面に多量の結晶水を含んでいるために、結合剤樹脂や溶剤とのなじみが悪く、所望の分散度が得られにくい。 In addition, when the goethite particle powder described in Patent Document 4 (Japanese Patent Laid-Open No. 10-334450) is used as the nonmagnetic powder for the nonmagnetic underlayer, the surface of the goethite particle powder contains a large amount of crystal water. For this reason, the compatibility with the binder resin and the solvent is poor, and it is difficult to obtain a desired degree of dispersion.
そこで、本発明は、表面平滑性に優れた磁気記録媒体の非磁性下地層用非磁性粒子粉末として好適な分散性及び充填性が優れていると共に、カレンダー処理による表面平滑性の向上が期待できるヘマタイト粒子粉末を得ることを技術的課題とする。 Therefore, the present invention is excellent in dispersibility and filling properties suitable as a nonmagnetic particle powder for a nonmagnetic underlayer of a magnetic recording medium excellent in surface smoothness, and can be expected to improve surface smoothness by calendering. Obtaining hematite 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、平均長軸径が0.005〜0.6μmであって平均短軸径が0.001〜0.40μmである紡錘状ヘマタイト粒子粉末であって、該ヘマタイト粒子粉末を構成する紡錘状ヘマタイト粒子の粒子端が開いていることを特徴とする磁気記録媒体の非磁性下地層用ヘマタイト粒子粉末である(本発明1)。 That is, the present invention provides a spindle-shaped hematite particle powder having an average major axis diameter of 0.005 to 0.6 μm and an average minor axis diameter of 0.001 to 0.40 μm. This is a hematite particle powder for a non-magnetic underlayer of a magnetic recording medium, wherein the end of the spindle-shaped hematite particles to be opened is open (Invention 1).
また、本発明は、本発明1の紡錘状ヘマタイト粒子粉末のBET比表面積値が100〜250m2/gであることを特徴とする請求項1記載の磁気記録媒体の非磁性下地層用ヘマタイト粒子粉末である(本発明2)。 Further, in the present invention, the spindle-shaped hematite particle powder of the present invention 1 has a BET specific surface area value of 100 to 250 m 2 / g. It is a powder (Invention 2).
また、本発明は、本発明1の紡錘状ヘマタイト粒子粉末のシクロヘキサノンの吸液量が0.6ml/g以上であることを特徴とする磁気記録媒体の非磁性下地層用ヘマタイト粒子粉末である(本発明3)。 The present invention also provides a hematite particle powder for a nonmagnetic underlayer of a magnetic recording medium, wherein the spindle-shaped hematite particle powder of the present invention 1 has a cyclohexanone absorption of 0.6 ml / g or more ( Invention 3).
また、本発明は、粒子の表面が、アルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれる少なくとも一種からなる表面被覆物によって被覆されていることを特徴とする本発明1乃至本発明3のいずれかの磁気記録媒体の非磁性下地層用ヘマタイト粒子粉末である(本発明4)。 Further, the present invention is characterized in that the surface of the particle is coated with a surface coating composed of at least one selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. This is a hematite particle powder for a nonmagnetic underlayer of the magnetic recording medium of any one of Inventions 1 to 3 (Invention 4).
また、本発明は、非磁性支持体、該非磁性支持体上に形成される非磁性粉末及び結合剤樹脂を含む非磁性下地層及び該非磁性下地層の上に形成される磁性粒子粉末及び結合剤樹脂を含む磁気記録層からなる磁気記録媒体において、前記非磁性粉末が本発明1乃至本発明4のいずれかに記載の非磁性下地層用ヘマタイト粒子粉末であることを特徴とする磁気記録媒体である(本発明5)。 The present invention also relates to a nonmagnetic support, a nonmagnetic underlayer comprising a nonmagnetic powder and a binder resin formed on the nonmagnetic support, and a magnetic particle powder and a binder formed on the nonmagnetic underlayer. A magnetic recording medium comprising a magnetic recording layer containing a resin, wherein the nonmagnetic powder is the hematite particle powder for a nonmagnetic underlayer according to any one of the first to fourth aspects of the present invention. There is (Invention 5).
また、本発明は、本発明5の磁気記録媒体において、磁性粒子粉末として、軸比が7.0以下の鉄を主成分とする紡錘状金属磁性粒子粉末を用いることを特徴とする磁気記録媒体である(本発明6)。 According to the present invention, in the magnetic recording medium of the present invention 5, a spindle-shaped metal magnetic particle powder whose main component is iron having an axial ratio of 7.0 or less is used as the magnetic particle powder. (Invention 6).
本発明に係る非磁性下地層用ヘマタイト粒子粉末を用いた場合、表面平滑性に優れた非磁性下地層を得ることができ、該非磁性下地層を用いて磁気記録媒体とした場合、表面平滑性に優れた磁気記録媒体とすることができるので、非磁性下地層を有する磁気記録媒体の非磁性下地層用ヘマタイト粒子粉末として好適である。 When the hematite particle powder for nonmagnetic underlayer according to the present invention is used, a nonmagnetic underlayer excellent in surface smoothness can be obtained. When the nonmagnetic underlayer is used as a magnetic recording medium, surface smoothness is obtained. Therefore, it is suitable as a hematite particle powder for a nonmagnetic underlayer of a magnetic recording medium having a nonmagnetic underlayer.
また、本発明に係る磁気記録媒体は、上述した通り、表面平滑性に優れているので高密度磁気記録媒体として好適である。 The magnetic recording medium according to the present invention is suitable as a high-density magnetic recording medium because it has excellent surface smoothness as described above.
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.
まず、本発明に係る非磁性下地層用ヘマタイト粒子粉末について述べる。 First, the hematite particle powder for nonmagnetic underlayer according to the present invention will be described.
本発明に係る非磁性下地層用ヘマタイト粒子粉末の平均長軸径は0.005〜0.6μmである。平均長軸径が0.6μmを超える場合には、粒子サイズが大きすぎるため、これを用いて非磁性下地層を形成した場合には、塗膜の表面平滑性が損なわれやすい。平均長軸径が0.005μm未満の場合には、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、非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。好ましくは0.0075〜0.45μm、より好ましくは0.01〜0.3μmである。 The average major axis diameter of the nonmagnetic underlayer hematite particle powder according to the present invention is 0.005 to 0.6 μm. When the average major axis diameter exceeds 0.6 μm, the particle size is too large. Therefore, when the nonmagnetic underlayer is formed using this, the surface smoothness of the coating film tends to be impaired. When the average major axis diameter is less than 0.005 μm, aggregation is likely to occur due to an increase in intermolecular force due to the refinement of the particles, so that dispersibility in the vehicle during the production of the nonmagnetic paint is reduced. Preferably it is 0.0075-0.45 micrometer, More preferably, it is 0.01-0.3 micrometer.
本発明に係る非磁性下地層用ヘマタイト粒子粉末の平均短軸径は0.00025〜0.3μmである。平均短軸径が0.00025μm未満の場合には、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、非磁性塗料の製造時におけるビヒクル中の分散性が低下する。平均短軸径が0.3μm以上の場合には、工業的に得ることが困難である。好ましくは0.0003〜0.20μm、より好ましくは0.0005〜0.15μmである。 The average minor axis diameter of the nonmagnetic underlayer hematite particle powder according to the present invention is 0.00025 to 0.3 μm. When the average minor axis diameter is less than 0.00025 μm, aggregation is likely to occur due to an increase in intermolecular force due to the refinement of the particles, so that dispersibility in the vehicle during the production of the nonmagnetic coating material is lowered. When the average minor axis diameter is 0.3 μm or more, it is difficult to obtain industrially. Preferably it is 0.0003-0.20 micrometer, More preferably, it is 0.0005-0.15 micrometer.
本発明に係る非磁性下地層用ヘマタイト粒子の軸比(平均長軸径と平均短軸径の比)(以下、「軸比」という。)は2〜20が好ましい。軸比が2未満の場合及び20を超える場合には、得られる非磁性下地層の塗膜強度が小さくなる。より好ましくは3〜18、更により好ましくは4〜15、最も好ましくは5〜10である。 As for the axial ratio (ratio of an average major axis diameter and an average minor axis diameter) (henceforth "axial ratio") of the hematite particle | grains for nonmagnetic underlayers concerning this invention, 2-20 are preferable. When the axial ratio is less than 2 or exceeds 20, the coating strength of the obtained nonmagnetic underlayer becomes small. More preferably 3-18, even more preferably 4-15, most preferably 5-10.
本発明に係る非磁性下地層用ヘマタイト粒子粉末を構成するヘマタイト粒子の粒子形状は、図1に示すとおり、粒子端が開いた状態である。図2に示す従来の紡錘状ヘマタイト粒子は、粒子端が閉じており、非磁性下地層中での充填性が低下する。 The particle shape of the hematite particles constituting the non-magnetic underlayer hematite particle powder according to the present invention is such that the particle ends are open as shown in FIG. The conventional spindle-shaped hematite particles shown in FIG. 2 have closed particle ends, and the filling properties in the nonmagnetic underlayer are reduced.
本発明に係る非磁性下地層用ヘマタイト粒子粉末を構成するヘマタイト粒子において、ヘマタイト粒子の短軸径(W)と該粒子の粒子端から長軸径の1/10の点(b)における粒子幅(Wb)との比(W/Wb)の平均値が1.20以上が好ましい。W/Wb比が1.20未満の場合には、該ヘマタイト粒子粉末を用いて非磁性下地層を形成した場合、非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。分散性を考慮した場合、好ましくは1.21〜3.0であり、より好ましくは1.22〜2.5である。 In the hematite particles constituting the hematite particle powder for a nonmagnetic underlayer according to the present invention, the particle width at the short axis diameter (W) of the hematite particles and the point (b) that is 1/10 of the long axis diameter from the particle end of the particles. The average value of the ratio (W / Wb) to (Wb) is preferably 1.20 or more. When the W / Wb ratio is less than 1.20, when the nonmagnetic underlayer is formed using the hematite particle powder, the dispersibility of the nonmagnetic coating material in the vehicle decreases. In consideration of dispersibility, it is preferably 1.21 to 3.0, more preferably 1.22 to 2.5.
本発明に係る非磁性下地層用ヘマタイト粒子粉末のBET比表面積値は90〜300m2/gであることが好ましい。BET比表面積値が300m2/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、非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。90m2/g未満の場合には、粒子サイズが大きすぎるため、塗膜の表面平滑性向上の観点から好ましくない。得られる磁気記録媒体の表面平滑性を考慮すれば、BET比表面積値は95〜275m2/gがより好ましく、更により好ましくは100〜250m2/gである。 The BET specific surface area value of the nonmagnetic underlayer hematite particle powder according to the present invention is preferably 90 to 300 m 2 / g. When the BET specific surface area value exceeds 300 m 2 / g, aggregation is likely to occur due to an increase in intermolecular force due to finer particles, so that the dispersibility in the vehicle during the production of the nonmagnetic coating material is lowered. When it is less than 90 m 2 / g, the particle size is too large, which is not preferable from the viewpoint of improving the surface smoothness of the coating film. Considering the surface smoothness of the magnetic recording medium obtained, BET specific surface area value is more preferably 95~275m 2 / g, and even more preferably 100 to 250 m 2 / g.
本発明に係る非磁性下地層用ヘマタイト粒子粉末のシクロヘキサノンの吸液量は0.6ml/g以上が好ましく、より好ましくは0.65〜1.5ml/gである。0.6ml/g未満の場合には、紡錘状ヘマタイト粒子の粒子端が閉じた状態であると推定され、非磁性下地層中での充填性が低下する。 The liquid absorption amount of cyclohexanone in the nonmagnetic underlayer hematite particles according to the present invention is preferably 0.6 ml / g or more, more preferably 0.65 to 1.5 ml / g. If it is less than 0.6 ml / g, it is presumed that the end of the spindle-shaped hematite particles is closed, and the filling property in the nonmagnetic underlayer is lowered.
本発明に係る非磁性下地層用ヘマタイト粒子粉末は、後述する測定方法で測定した塗膜収縮率が8.0〜20%が好ましい。塗膜の収縮率が8.0%未満の場合には、カレンダー処理による十分な表面平滑効果が得られない。また、20%を超える場合には、塗膜の膜厚の変動が大きいため、磁気記録媒体の設計が困難となる。より好ましくは8.5〜19%であり、より好ましくは9.0〜18%である。 The non-magnetic underlayer hematite particle powder according to the present invention preferably has a coating film shrinkage of 8.0 to 20% as measured by the measurement method described below. When the contraction rate of the coating film is less than 8.0%, a sufficient surface smoothing effect by the calendar process cannot be obtained. On the other hand, if it exceeds 20%, the film thickness of the coating film varies greatly, making it difficult to design a magnetic recording medium. More preferably, it is 8.5-19%, More preferably, it is 9.0-18%.
本発明に係る非磁性下地層用ヘマタイト粒子粉末は、必要により、ヘマタイト粒子粉末の表面がアルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれる少なくとも1種からなる表面被覆物によって被覆されていてもよい。表面が表面被覆物で被覆されているヘマタイト粒子粉末は、ビヒクル中に分散させる場合に、結合剤樹脂とのなじみがよく、所望の分散度が得られ易い。 The hematite particle powder for a nonmagnetic underlayer according to the present invention is at least one selected from the group consisting of an aluminum hydroxide, an aluminum oxide, a silicon hydroxide and a silicon oxide, if necessary. You may coat | cover with the surface coating which consists of. The hematite particle powder, the surface of which is coated with a surface coating, is well-familiar with the binder resin when dispersed in a vehicle, and a desired degree of dispersion is easily obtained.
前記表面被覆物の量は、ヘマタイト粒子粉末に対してアルミニウムの水酸化物やアルミニウムの酸化物はAl換算で、ケイ素の水酸化物やケイ素の酸化物はSiO2換算で、それぞれ0.01〜50重量%が好ましい。0.01重量%未満の場合には、被覆による分散性向上効果がほとんどなく、50重量%を超える場合には、被覆効果が飽和するため、必要以上に被覆する意味がない。ビヒクル中における分散性向上効果及び工業的な生産性を考慮すれば、0.05〜20重量%がより好ましい。 The amount of the surface coating is 0.01 to each of aluminum hydroxide and aluminum oxide in terms of Al, and silicon hydroxide and silicon oxide in terms of SiO 2 with respect to the hematite particle powder. 50% by weight is preferred. When the amount is less than 0.01% by weight, there is almost no effect of improving dispersibility by coating. Considering the effect of improving dispersibility in the vehicle and industrial productivity, 0.05 to 20% by weight is more preferable.
アルミニウム化合物とケイ素化合物とを併せて使用する場合には、ヘマタイト粒子粉末に対してAl換算量とSiO2換算量との総和で0.01〜50重量%が好ましい。 When used in conjunction with an aluminum compound and a silicon compound, 0.01 to 50 wt% in total of Al equivalent amount and SiO 2 equivalent amount with respect to hematite particles are preferred.
本発明に係る表面被覆物で被覆されているヘマタイト粒子粉末は、表面被覆物で被覆されていない本発明に係るヘマタイト粒子粉末とほぼ同程度の粒子サイズ及びBET比表面積値を有している。 The hematite particle powder coated with the surface coating according to the present invention has a particle size and a BET specific surface area value substantially the same as those of the hematite particle powder according to the present invention which is not coated with the surface coating.
本発明に係る非磁性下地層用ヘマタイト粒子粉末は、粒子内部にアルミニウムを含有させてもよい。粒子内部にアルミニウムを含有させたヘマタイト粒子を用いることによって、得られる磁気記録媒体の耐久性が向上する。粒子内部に含有させるアルミニウム量は、Al換算で0.05〜50重量%が好ましく、より好ましくは0.05〜40重量%である。 The hematite particle powder for nonmagnetic underlayer according to the present invention may contain aluminum inside the particle. By using hematite particles containing aluminum inside the particles, the durability of the obtained magnetic recording medium is improved. The amount of aluminum contained inside the particles is preferably 0.05 to 50% by weight, more preferably 0.05 to 40% by weight in terms of Al.
殊に、磁気記録媒体の耐腐食性を考慮した場合には、ヘマタイト粒子粉末中の可溶性ナトリウム塩、可溶性硫酸塩等の含有量を低減した高純度化したヘマタイト粒子粉末が好ましい。 In particular, in consideration of the corrosion resistance of the magnetic recording medium, highly purified hematite particle powder in which the content of soluble sodium salt, soluble sulfate, etc. in the hematite particle powder is reduced is preferable.
高純度化したヘマタイト粒子粉末は、可溶性ナトリウム塩の含有量がNa換算で300ppm以下が好ましく、より好ましくは200ppmである。また、可溶性硫酸塩の含有量はSO4換算で150ppm以下が好ましく、より好ましくは100ppm以下である。また、粉体pH値は8.0以上が好ましい。 The highly purified hematite particle powder preferably has a soluble sodium salt content of 300 ppm or less, more preferably 200 ppm in terms of Na. Further, the content of soluble sulfate is preferably 150 ppm or less, more preferably 100 ppm or less in terms of SO 4 . The powder pH value is preferably 8.0 or more.
次に、本発明に係る非磁性下地層用ヘマタイト粒子粉末の製造法について述べる。 Next, a method for producing a hematite particle powder for a nonmagnetic underlayer according to the present invention will be described.
本発明に係る非磁性下地層用ヘマタイト粒子粉末は、紡錘状ゲータイト粒子を摩砕処理した後、200〜540℃の温度範囲で加熱脱水処理して得ることができる。 The hematite particle powder for nonmagnetic underlayer according to the present invention can be obtained by subjecting spindle-shaped goethite particles to grinding treatment and then heat dehydration treatment in a temperature range of 200 to 540 ° C.
本発明における紡錘状ゲータイト粒子粉末は、通常の方法によって得ることができ、例えば、第一鉄塩と炭酸アルカリ水溶液又は水酸化アルカリ・炭酸アルカリ水溶液のいずれかの水溶液を用いて反応して得られる鉄含有沈殿物を含む懸濁液に空気等の酸素含有ガスを通気して得ることができる。 The spindle-shaped goethite particle powder in the present invention can be obtained by a usual method, for example, obtained by reacting with a ferrous salt and an aqueous solution of an alkali carbonate aqueous solution or an alkali hydroxide / alkali carbonate aqueous solution. An oxygen-containing gas such as air can be aerated through the suspension containing the iron-containing precipitate.
紡錘状ゲータイト粒子粉末としては、平均長軸径が0.007〜0.80μm、平均短軸径が0.001〜0.35μm、軸比が2〜20であることが好ましい。 The spindle-shaped goethite particles preferably have an average major axis diameter of 0.007 to 0.80 μm, an average minor axis diameter of 0.001 to 0.35 μm, and an axial ratio of 2 to 20.
尚、必要により、紡錘状ゲータイト粒子の粒子表面にP、Si、B、Zr、Sb等の焼結防止剤を被覆処理してもよい。 If necessary, the surface of the spindle-shaped goethite particles may be coated with a sintering inhibitor such as P, Si, B, Zr, or Sb.
紡錘状ゲータイト粒子の摩砕処理は、前記紡錘状ゲータイト粒子の生成反応で得られる紡錘状ゲータイト粒子を含有する懸濁液を濾別、水洗した湿ケーキを再度水に分散させた紡錘状ゲータイト粒子を含有する懸濁液、又は前記紡錘状ゲータイト粒子の生成反応で得られる紡錘状ゲータイト粒子を含有する懸濁液を濾別、水洗、乾燥して紡錘状ゲータイト粒子粉末として取り出した後、再度水に分散させた紡錘状ゲータイト粒子を含有する水懸濁液を用いてもよい。好ましくは紡錘状ゲータイト粒子の湿ケーキを再度水に分散させた紡錘状ゲータイト粒子を含有する懸濁液を用いることが好ましい。 Spindle-shaped goethite particles are ground by spinning the suspension containing the spindle-shaped goethite particles obtained by the reaction of forming the spindle-shaped goethite particles, and the wet cake washed with water and dispersed again in water. Or a suspension containing the spindle-shaped goethite particles obtained by the reaction for producing the spindle-shaped goethite particles is filtered off, washed with water, dried, and taken out as spindle-shaped goethite particle powder. An aqueous suspension containing spindle-shaped goethite particles dispersed in may be used. It is preferable to use a suspension containing spindle-shaped goethite particles in which a wet cake of spindle-like goethite particles is dispersed again in water.
紡錘状ゲータイト粒子の摩砕処理は、紡錘状ゲータイト粒子を含むスラリーの濃度を30〜500g/l、好ましくは40〜250g/l、より好ましくは50〜200g/lに調製した後、スラリーに回転数1000〜9000rpm、好ましくは1200〜5000rpmのせん断力をかけて摩砕することによって行う。 The grinding treatment of the spindle-shaped goethite particles is carried out by adjusting the concentration of the slurry containing the spindle-shaped goethite particles to 30 to 500 g / l, preferably 40 to 250 g / l, more preferably 50 to 200 g / l, and then rotating the slurry. It is carried out by grinding by applying a shearing force of several thousand to 9000 rpm, preferably 1200 to 5000 rpm.
紡錘状ゲータイト粒子を含むスラリーを摩砕するための機器としては、スラリーにせん断力を加えることのできる装置が好ましく、例えば、摩砕微粒化機、超微粒磨砕機といった湿式摩砕機等を用いることができる。 As an apparatus for grinding a slurry containing spindle-shaped goethite particles, an apparatus capable of applying a shearing force to the slurry is preferable. For example, a wet grinding machine such as a grinding atomizer or an ultrafine grinding machine is used. Can do.
上記湿式摩砕機としては、具体的に、スーパーマスコロイダー、セレンディピター(増幸産業株式会社製)及びT.K.マイコローダーM型(特殊機化工業株式会社)等がある。 Specific examples of the wet mill include supermass colloiders, serendipeaters (manufactured by Masuko Sangyo Co., Ltd.), and T.C. K. There are Myco Loader M type (Special Machine Industry Co., Ltd.).
次いで、摩砕処理後の紡錘状ゲータイト粒子粉末を200〜540℃の温度範囲で加熱処理してヘマタイト粒子粉末とする。加熱温度が200℃未満の場合には脱水反応に長時間を要するため好ましくない。540℃を超える場合には脱水反応が急激に生起し、粒子の形状が崩れやすくなったり、粒子相互間の焼結を引き起こすことになり好ましくない。加熱処理の温度は、好ましくは250〜500℃、より好ましくは280〜450℃である。また、加熱処理時間は30分〜3時間が好ましい。 Next, the spindle-shaped goethite particle powder after the grinding treatment is heat-treated in a temperature range of 200 to 540 ° C. to obtain a hematite particle powder. When the heating temperature is less than 200 ° C., it takes a long time for the dehydration reaction. When the temperature exceeds 540 ° C., the dehydration reaction occurs abruptly, and the shape of the particles tends to be collapsed or sintering between the particles is not preferable. The temperature of the heat treatment is preferably 250 to 500 ° C, more preferably 280 to 450 ° C. The heat treatment time is preferably 30 minutes to 3 hours.
高純度化されたヘマタイト粒子粉末は、摩砕処理後、加熱処理したヘマタイト粒子粉末をアルカリ水溶液中で加熱処理し、濾別、水洗することにより得ることができる。 The highly purified hematite particle powder can be obtained by subjecting the heat-treated hematite particle powder to heat treatment in an alkaline aqueous solution after filtration, filtering and washing with water.
アルカリ水溶液のpH値は13.0以上が好ましい。加熱処理の温度は80℃以上が好ましく、より好ましくは90℃以上である。 The pH value of the alkaline aqueous solution is preferably 13.0 or more. The temperature of the heat treatment is preferably 80 ° C. or higher, more preferably 90 ° C. or higher.
本発明における表面被覆物により被覆されたヘマタイト粒子粉末は、摩砕処理後、加熱処理して得られたヘマタイト粒子粉末を分散して得られる水懸濁液に、アルミニウム化合物、ケイ素化合物又は当該両化合物を添加して混合攪拌することにより、又は、必要により、混合攪拌後にpH値を調整することにより、前記ヘマタイト粒子粉末の粒子表面を、アルミニウムの水酸化物、アルミニウムの酸化物、ケイ素の水酸化物及びケイ素の酸化物から選ばれる一種又は二種以上の化合物で被覆し、次いで、濾別、水洗、乾燥、粉砕する。必要により、更に、脱気・圧密処理等を施してもよい。 The hematite particle powder coated with the surface coating in the present invention is obtained by dispersing the hematite particle powder obtained by the heat treatment after the grinding treatment, in an aqueous suspension obtained by dispersing the aluminum compound, the silicon compound, or both of them. By adding a compound and mixing and stirring, or if necessary, adjusting the pH value after mixing and stirring, the particle surface of the hematite particle powder is mixed with aluminum hydroxide, aluminum oxide, silicon water. It coat | covers with the 1 type, or 2 or more types of compound chosen from the oxide and the oxide of a silicon | silicone, Then, it filters, wash | cleans, dries, and grind | pulverizes. If necessary, a deaeration / consolidation process may be further performed.
アルミニウム化合物としては、酢酸アルミニウム、硫酸アルミニウム、塩化アルミニウム、硝酸アルミニウム等のアルミニウム塩や、アルミン酸ナトリウム等のアルミン酸アルカリ塩等が使用できる。ケイ素化合物としては、3号水ガラス、オルトケイ酸ナトリウム、メタケイ酸ナトリウム等が使用できる。 As the aluminum compound, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride, and aluminum nitrate, and alkali aluminates such as sodium aluminate can be used. As the silicon compound, No. 3 water glass, sodium orthosilicate, sodium metasilicate and the like can be used.
次に、本発明に係る磁気記録媒体について述べる。 Next, the magnetic recording medium according to the present invention will be described.
本発明に係る磁気記録媒体は、非磁性支持体、該非磁性支持体上に形成された非磁性下地層及び該非磁性下地層上に形成された磁気記録層とからなる。 The magnetic recording medium according to the present invention comprises a nonmagnetic support, a nonmagnetic underlayer formed on the nonmagnetic support, and a magnetic recording layer formed on the nonmagnetic underlayer.
前記非磁性支持体としては、現在、磁気記録媒体に汎用されているポリエチレンテレフタレート、ポリエチレン、ポリプロピレン、ポリカーボネート、ポリエチレンナフタレート、ポリアミド、ポリアミドイミド、ポリイミド等の合成樹脂フィルム、アルミニウム、ステンレス等金属の箔や板及び各種の紙を使用することができる。その厚みは、材質により種々異なるが、通常好ましくは1.0〜300μm、より好ましくは2.0〜200μmである。 Examples of the nonmagnetic support include polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, synthetic resin films such as polyamide, polyamideimide, and polyimide, which are widely used for magnetic recording media, and metal foils such as aluminum and stainless steel. A board and various types of paper can be used. The thickness varies depending on the material, but is usually preferably 1.0 to 300 μm, more preferably 2.0 to 200 μm.
なお、磁気ディスクの場合には、一般にポリエチレンテレフタレートが用いられ、その厚みは、通常50〜300μm、好ましくは60〜200μmである。磁気テープの場合には、ポリエチレンテレフタレート、ポリエチレンナフタレート、ポリアミドなどが用いられ、ポリエチレンテレフタレートの厚みは、通常3〜100μm、好ましくは4〜20μm、ポリエチレンナフタレートの厚みは、通常3〜50μm、好ましくは4〜20μm、ポリアミドの厚みは、通常2〜10μm、好ましくは3〜7μmである。 In the case of a magnetic disk, polyethylene terephthalate is generally used, and its thickness is usually 50 to 300 μm, preferably 60 to 200 μm. In the case of a magnetic tape, polyethylene terephthalate, polyethylene naphthalate, polyamide or the like is used. The thickness of polyethylene terephthalate is usually 3 to 100 μm, preferably 4 to 20 μm, and the thickness of polyethylene naphthalate is usually 3 to 50 μm, preferably Is 4 to 20 μm, and the thickness of polyamide is usually 2 to 10 μm, preferably 3 to 7 μm.
本発明における非磁性下地層は、本発明に係る非磁性下地層用ヘマタイト粒子粉末又は本発明に係る表面被覆物で被覆されている非磁性下地層用ヘマタイト粒子粉末及び結合剤樹脂からなる。 The nonmagnetic underlayer in the present invention comprises the nonmagnetic underlayer hematite particle powder according to the present invention or the nonmagnetic underlayer hematite particle powder coated with the surface coating according to the present invention and a binder resin.
結合剤樹脂としては、現在、磁気記録媒体の製造にあたって汎用されている塩化ビニル−酢酸ビニル共重合体、ウレタン樹脂、塩化ビニル−酢酸ビニル−マレイン酸共重合体、ウレタンエラストマー、ブタジエン−アクリロニトリル共重合体、ポリビニルブチラール、ニトロセルロース等セルロース誘導体、ポリエステル樹脂、ポリブタジエン等の合成ゴム系樹脂、エポキシ樹脂、ポリアミド樹脂、ポリイソシアネート、電子線硬化型アクリルウレタン樹脂等及びこれらの混合物を使用することができる。また、各結合剤樹脂には−OH、−COOH、−SO3M、−OPO2M2、−NH2等の極性基(但し、MはH、Na、Kである。)が含まれていてもよい。ヘマタイト粒子粉末及び磁性粒子粉末のビヒクル中における分散性を考慮すれば、極性基として−COOH、−SO3Mが含まれている結合剤樹脂が好ましい。 As binder resins, vinyl chloride-vinyl acetate copolymer, urethane resin, vinyl chloride-vinyl acetate-maleic acid copolymer, urethane elastomer, butadiene-acrylonitrile copolymer, which are currently widely used in the production of magnetic recording media, are used. Polymers, cellulose derivatives such as polyvinyl butyral, nitrocellulose, synthetic rubber resins such as polyester resins and polybutadiene, epoxy resins, polyamide resins, polyisocyanates, electron beam curable acrylic urethane resins, and mixtures thereof can be used. Each binder resin contains polar groups such as —OH, —COOH, —SO 3 M, —OPO 2 M 2 , —NH 2 (where M is H, Na, K). May be. Considering the dispersibility of the hematite particle powder and magnetic particle powder in the vehicle, a binder resin containing —COOH and —SO 3 M as polar groups is preferable.
本発明におけるヘマタイト粒子粉末と結合剤樹脂との配合割合は、結合剤樹脂100重量部に対してヘマタイト粒子粉末が5〜2000重量部、好ましくは100〜1000重量部である。 The blending ratio of the hematite particle powder and the binder resin in the present invention is 5 to 2000 parts by weight, preferably 100 to 1000 parts by weight of the hematite particle powder with respect to 100 parts by weight of the binder resin.
ヘマタイト粒子粉末が5重量部未満の場合には、非磁性塗料中のヘマタイト粒子粉末が少なすぎるため、塗膜を形成した時に、ヘマタイト粒子粉末の連続分散した層が得られず、塗膜表面の平滑性及び塗膜の強度が不十分となる。2000重量部を超える場合には、結合剤樹脂の量に対してヘマタイト粒子粉末が多すぎるため、非磁性塗料中でヘマタイト粒子粉末が十分に分散されず、その結果、塗膜を形成した時に、十分な表面平滑性を有する塗膜が得られ難い。また、ヘマタイト粒子粉末が結合剤樹脂によって十分にバインドされないため、得られた塗膜はもろいものとなりやすい。 When the hematite particle powder is less than 5 parts by weight, the amount of hematite particle powder in the non-magnetic coating is too small, and when the coating film is formed, a continuously dispersed layer of hematite particle powder cannot be obtained. The smoothness and the strength of the coating film are insufficient. When the amount exceeds 2000 parts by weight, the amount of hematite particle powder is too much with respect to the amount of the binder resin, so that the hematite particle powder is not sufficiently dispersed in the nonmagnetic paint, and as a result, when a coating film is formed, It is difficult to obtain a coating film having sufficient surface smoothness. Further, since the hematite particle powder is not sufficiently bound by the binder resin, the obtained coating film tends to be brittle.
非磁性支持体上に形成された非磁性下地層の塗膜厚さは、0.2〜10μmであることが好ましい。0.2μm未満の場合には、非磁性支持体の表面粗さを改善することが困難となり、強度も不十分となりやすい。磁気記録媒体の薄層化及び塗膜の強度を考慮すれば、塗膜厚さはより好ましくは0.5〜5μmである。 The coating thickness of the nonmagnetic underlayer formed on the nonmagnetic support is preferably 0.2 to 10 μm. When it is less than 0.2 μm, it is difficult to improve the surface roughness of the nonmagnetic support, and the strength tends to be insufficient. Considering the thinning of the magnetic recording medium and the strength of the coating film, the coating film thickness is more preferably 0.5 to 5 μm.
なお、非磁性下地層に、磁気記録媒体の製造に通常用いられている潤滑剤、研磨剤、帯電防止剤等を添加してもよい。 Note that a lubricant, an abrasive, an antistatic agent, and the like that are usually used in the manufacture of magnetic recording media may be added to the nonmagnetic underlayer.
本発明1乃至3のヘマタイト粒子粉末を用いた非磁性下地層は、塗膜の光沢度が182〜300%、好ましくは187〜300%であって、塗膜表面粗度Raが0.5〜7.5nm、好ましくは0.5〜7.3nmであって、塗膜の強度は、ヤング率(相対値)が126〜160、好ましくは128〜160であり、塗膜の収縮率は8.0〜20%、好ましくは8.5〜19%、より好ましくは9.0〜18%である。 The nonmagnetic underlayer using the hematite particle powder of the present invention 1 to 3 has a coating film glossiness of 182-300%, preferably 187-300%, and a coating film surface roughness Ra of 0.5- The strength of the coating film is 7.5 nm, preferably 0.5 to 7.3 nm. The Young's modulus (relative value) of the coating film is 126 to 160, preferably 128 to 160, and the contraction ratio of the coating film is 8. It is 0 to 20%, preferably 8.5 to 19%, more preferably 9.0 to 18%.
本発明4のヘマタイト粒子粉末を用いた非磁性下地層は、塗膜の光沢度が187〜300%、好ましくは192〜300%であって、塗膜表面粗度Raが0.5〜7.3nm、好ましくは0.5〜7.0nmであって、塗膜の強度は、ヤング率(相対値)が128〜160、好ましくは130〜160であり、塗膜の収縮率は8.5〜20%、好ましくは9.0〜19%、より好ましくは10.5〜18%である。 The nonmagnetic underlayer using the hematite particle powder of the present invention 4 has a coating film glossiness of 187 to 300%, preferably 192 to 300%, and a coating film surface roughness Ra of 0.5 to 7. The strength of the coating film is 3 nm, preferably 0.5 to 7.0 nm, and the Young's modulus (relative value) is 128 to 160, preferably 130 to 160, and the contraction rate of the coating film is 8.5 to 20%, preferably 9.0 to 19%, more preferably 10.5 to 18%.
本発明における磁気記録層は、磁性粒子粉末及び結合剤樹脂からなる。 The magnetic recording layer in the present invention comprises magnetic particle powder and binder resin.
磁性粒子粉末としては、マグヘマイト粒子粉末(γ−Fe2O3)やマグネタイト粒子粉末(FeO x・Fe2O3、0<x≦1)等の磁性酸化鉄粒子粉末にCo又はCo及びFeを被着させたCo被着型磁性酸化鉄粒子粉末、前記Co被着型磁性酸化鉄粒子粉末にFe以外のCo、Al、Ni、P、Zn、Si、B、希土類金属等の異種元素を含有させたCo被着型磁性酸化鉄粒子粉末、鉄を主成分とする針状金属磁性粒子粉末、鉄以外のCo、Al、Ni、P、Zn、Si、B、希土類金属等を含有する針状鉄合金磁性粒子粉末、Ba、Sr、又はBa−Srを含有するマグネトプランバイト型板状フェライト粒子粉末並びにこれらにCo、Ni、Zn、Mn、Mg、Ti、Sn、Zr、Nb、Cu、Mo等の2価及び4価の金属から選ばれた保磁力低減剤の1種又は2種以上を含有させた板状マグネトプランバイト型フェライト粒子粉末等のいずれかを用いることができる。 As magnetic particle powder, Co or Co and Fe are added to magnetic iron oxide particle powder such as maghemite particle powder (γ-Fe 2 O 3 ) and magnetite particle powder ( FeO x · Fe 2 O 3 , 0 <x ≦ 1). Co-coated magnetic iron oxide particle powder deposited, and the Co-coated magnetic iron oxide particle powder contains different elements such as Co, Al, Ni, P, Zn, Si, B, rare earth metals other than Fe Co-coated magnetic iron oxide particle powder, acicular metal magnetic particle powder containing iron as a main component, acicular shape containing Co, Al, Ni, P, Zn, Si, B, rare earth metal, etc. other than iron Iron alloy magnetic particle powder, magnetoplumbite type plate-like ferrite particle powder containing Ba, Sr or Ba-Sr, and Co, Ni, Zn, Mn, Mg, Ti, Sn, Zr, Nb, Cu, Mo Divalent and tetravalent metals such as It can be used any of such plate-type ferrite particles which contains one or more al selected coercivity reducing agent.
なお、近年の短波長記録、高密度記録を考慮すれば、鉄を主成分とする針状金属磁性粒子粉末、鉄以外のCo、Al、Ni、P、Zn、Si、B、希土類金属等を含有する針状鉄合金磁性粒子粉末等が好ましい。 In consideration of recent short-wavelength recording and high-density recording, acicular metal magnetic particle powder mainly composed of iron, Co, Al, Ni, P, Zn, Si, B, rare earth metals, etc. other than iron The acicular iron alloy magnetic particle powder contained is preferable.
磁性粒子粉末は、平均長軸径(板状粒子の場合は平均板面径)が0.01〜0.5μm、好ましくは0.03〜0.3μmである。該磁性粒子粉末の粒子形状は針状もしくは板状が好ましい。ここで「針状」とは、文字通りの針状はもちろん、紡錘状や米粒状などを含む意味である。 The magnetic particle powder has an average major axis diameter (average plate surface diameter in the case of plate-like particles) of 0.01 to 0.5 μm, preferably 0.03 to 0.3 μm. The particle shape of the magnetic particle powder is preferably a needle shape or a plate shape. Here, the “needle shape” means not only a literal needle shape but also a spindle shape or a rice grain shape.
また、磁性粒子粉末の粒子形状が針状の場合、軸比は3以上、好ましくは5以上であり、ビヒクル中における分散性を考慮すれば、その上限値は15であり、好ましくは10である。更に、磁気記録層中の磁性粒子粉末の充填率を考慮すれば、軸比は7.0以下が好ましい。 Further, when the particle shape of the magnetic particle powder is needle-shaped, the axial ratio is 3 or more, preferably 5 or more, and the upper limit is 15 and preferably 10 considering the dispersibility in the vehicle. . Further, the axial ratio is preferably 7.0 or less in consideration of the filling rate of the magnetic particle powder in the magnetic recording layer.
磁性粒子粉末の粒子形状が板状の場合、板状比(平均板面径と平均厚みの比)(以下、「板状比」という。)は2以上、好ましくは3以上であり、ビヒクル中における分散性を考慮すれば、その上限値は50であり、好ましくは45である。 When the particle shape of the magnetic particle powder is plate-like, the plate-like ratio (ratio of average plate surface diameter to average thickness) (hereinafter referred to as “plate-like ratio”) is 2 or more, preferably 3 or more. The upper limit is 50, preferably 45, taking into account the dispersibility at.
磁性粒子粉末の磁気特性は、保磁力値が39.8〜318.3kA/m(500〜4000Oe)、好ましくは43.8〜318.3kA/m(550〜4000Oe)であって、飽和磁化値が50〜170Am2/kg(50〜170emu/g)、好ましくは60〜170Am2/kg(60〜170emu/g)である。 The magnetic properties of the magnetic particle powder include a coercive force value of 39.8 to 318.3 kA / m (500 to 4000 Oe), preferably 43.8 to 318.3 kA / m (550 to 4000 Oe), and a saturation magnetization value. Is 50 to 170 Am 2 / kg (50 to 170 emu / g), preferably 60 to 170 Am 2 / kg (60 to 170 emu / g).
高密度記録化等を考慮して、磁性粒子粉末として鉄を主成分とする針状金属磁性粒子粉末又は針状鉄合金磁性粒子粉末を用いた場合の磁気特性は、保磁力値が63.7〜278.5kA/m(800〜3500Oe)、好ましくは71.6〜278.5kA/m(900〜3500Oe)、飽和磁化値が90〜170Am2/kg(90〜170emu/g)、好ましくは100〜170Am2/kg(100〜170emu/g)である。 In consideration of high-density recording and the like, the magnetic characteristics when the acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly containing iron is used as the magnetic particle powder have a coercive force value of 63.7. 278.5 kA / m (800-3500 Oe), preferably 71.6-278.5 kA / m (900-3500 Oe), saturation magnetization value 90-170 Am 2 / kg (90-170 emu / g), preferably 100 -170 Am < 2 > / kg (100-170 emu / g).
結合剤樹脂としては、前記非磁性下地層を形成するために用いた結合剤樹脂を使用することができる。 As the binder resin, the binder resin used for forming the nonmagnetic underlayer can be used.
非磁性下地層上に設けられた磁気記録層の塗膜厚さは、0.01〜5μmの範囲である。0.01μm未満の場合には、均一な塗布が困難であり、塗りむら等の現象が出やすくなるため好ましくない。5μmを超える場合には、反磁界の影響のため、所望の電磁変換特性が得られにくくなる。好ましくは0.05〜1μmの範囲である。 The coating thickness of the magnetic recording layer provided on the nonmagnetic underlayer is in the range of 0.01 to 5 μm. If it is less than 0.01 μm, uniform coating is difficult, and phenomena such as uneven coating tend to occur, which is not preferable. When it exceeds 5 μm, it is difficult to obtain desired electromagnetic characteristics due to the influence of the demagnetizing field. Preferably it is the range of 0.05-1 micrometer.
磁性粒子粉末と結合剤樹脂との配合割合は、結合剤樹脂100重量部に対して磁性粒子粉末が200〜2000重量部、好ましくは300〜1500重量部である。 The blending ratio of the magnetic particle powder and the binder resin is 200 to 2000 parts by weight, preferably 300 to 1500 parts by weight, based on 100 parts by weight of the binder resin.
磁気記録層中には、通常用いられている潤滑剤、研磨剤、帯電防止剤等を添加してもよい。 In the magnetic recording layer, commonly used lubricants, abrasives, antistatic agents and the like may be added.
本発明に係る磁気記録媒体は、磁性粒子粉末として前記磁性粒子粉末を用い、非磁性下地層用非磁性粉末として本発明1乃至3のいずれかの非磁性下地層用ヘマタイト粒子粉末を用いた場合には、保磁力値が39.8〜318.3kA/m(500〜4000Oe)、好ましくは43.8〜318.3kA/m(550〜4000Oe)、角形比(残留磁束密度Br/飽和磁束密度Bm)が0.85〜0.95、好ましくは0.86〜0.95、塗膜の光沢度が172〜300%、好ましくは177〜300%、塗膜表面粗度Raが7.8nm以下、好ましくは2.0〜7.3nm、ヤング率(相対値)が128〜160、好ましくは130〜160である。また、後述する評価法による非磁性下地層と磁気記録層とからなる塗膜の収縮率は7.5〜18%、好ましくは8.0〜17%、より好ましくは8.5〜16%である。 The magnetic recording medium according to the present invention uses the magnetic particle powder as a magnetic particle powder, and the hematite particle powder for a nonmagnetic underlayer according to any one of the present invention 1 to 3 as a nonmagnetic powder for a nonmagnetic underlayer. Includes a coercive force value of 39.8 to 318.3 kA / m (500 to 4000 Oe), preferably 43.8 to 318.3 kA / m (550 to 4000 Oe), and a squareness ratio (residual magnetic flux density Br / saturated magnetic flux density). Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, the glossiness of the coating film is 172 to 300%, preferably 177 to 300%, and the coating film surface roughness Ra is 7.8 nm or less. The Young's modulus (relative value) is preferably 2.0 to 7.3 nm and 128 to 160, preferably 130 to 160. Further, the shrinkage ratio of the coating film composed of the nonmagnetic underlayer and the magnetic recording layer according to the evaluation method described later is 7.5 to 18%, preferably 8.0 to 17%, more preferably 8.5 to 16%. is there.
本発明に係る磁気記録媒体は、磁性粒子粉末として前記磁性粒子粉末を用い、非磁性下地層用非磁性粉末として本発明4の非磁性下地層用ヘマタイト粒子粉末を用いた場合には、保磁力値が39.8〜318.3kA/m(500〜4000Oe)、好ましくは39.8〜318.3kA/m(550〜4000Oe)、角形比(残留磁束密度Br/飽和磁束密度Bm)が0.85〜0.95、好ましくは0.86〜0.95、塗膜の光沢度が177〜300%、好ましくは182〜300%、塗膜表面粗度Raが7.3nm以下、好ましくは2.0〜7.0nm、ヤング率(相対値)が130〜160、好ましくは132〜160である。また、後述する評価法による非磁性下地層と磁気記録層とからなる塗膜の収縮率は7.5〜18%、好ましくは8.0〜17%、より好ましくは8.5〜16%である。 The magnetic recording medium according to the present invention uses the magnetic particle powder as the magnetic particle powder, and the coercive force when the nonmagnetic underlayer hematite particle powder of the present invention 4 is used as the nonmagnetic underlayer nonmagnetic powder. The value is 39.8 to 318.3 kA / m (500 to 4000 Oe), preferably 39.8 to 318.3 kA / m (550 to 4000 Oe), and the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0. 85 to 0.95, preferably 0.86 to 0.95, the glossiness of the coating film is 177 to 300%, preferably 182 to 300%, and the coating film surface roughness Ra is 7.3 nm or less, preferably 2. The Young's modulus (relative value) is 0 to 7.0 nm and 130 to 160, preferably 132 to 160. Further, the shrinkage ratio of the coating film composed of the nonmagnetic underlayer and the magnetic recording layer according to the evaluation method described later is 7.5 to 18%, preferably 8.0 to 17%, more preferably 8.5 to 16%. is there.
高密度記録等を考慮して、磁性粒子粉末として鉄を主成分とする針状金属磁性粒子粉末又は針状鉄合金磁性粒子粉末を用い、非磁性下地層用非磁性粉末として本発明1乃至3のいずれかの非磁性下地層用ヘマタイト粒子粉末を用いた場合には、保磁力値が63.7〜278.5kA/m(800〜3500Oe)、好ましくは71.6〜278.5kA/m(900〜3500Oe)、角形比(残留磁束密度Br/飽和磁束密度Bm)が0.86〜0.95、好ましくは0.87〜0.95、塗膜の光沢度が202〜300%、好ましくは207〜300%、塗膜表面粗度Raが6.8nm以下、好ましくは2.0〜6.3nm、ヤング率(相対値)が128〜160、好ましくは130〜160である。また、後述する評価法による非磁性下地層と磁気記録層とからなる塗膜の収縮率は7.5〜18%、好ましくは8.0〜17%、より好ましくは8.5〜16%である。 In consideration of high density recording or the like, the present invention 1 to 3 are used as nonmagnetic powders for nonmagnetic underlayers by using acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly composed of iron as magnetic particle powder. When the nonmagnetic underlayer hematite particle powder is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 3500 Oe), preferably 71.6 to 278.5 kA / m ( 900 to 3500 Oe), the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.86 to 0.95, preferably 0.87 to 0.95, and the glossiness of the coating film is 202 to 300%, preferably The coating film surface roughness Ra is 6.8 nm or less, preferably 2.0 to 6.3 nm, and the Young's modulus (relative value) is 128 to 160, preferably 130 to 160. Further, the shrinkage ratio of the coating film composed of the nonmagnetic underlayer and the magnetic recording layer according to the evaluation method described later is 7.5 to 18%, preferably 8.0 to 17%, more preferably 8.5 to 16%. is there.
磁性粒子粉末として鉄を主成分とする針状金属磁性粒子粉末又は針状鉄合金磁性粒子粉末を用い、非磁性下地層用非磁性粉末として表面被覆物によって被覆されている本発明に係る非磁性下地層用ヘマタイト粒子粉末を用いた場合には、保磁力値が63.7〜278.5kA/m(800〜3500Oe)、好ましくは71.6〜278.5kA/m(900〜3500Oe)、角形比(残留磁束密度Br/飽和磁束密度Bm)が0.87〜0.95、好ましくは0.88〜0.95、塗膜の光沢度が207〜300%、好ましくは212〜300%、塗膜表面粗度Raが6.3nm以下、好ましくは2.0〜5.8nm、ヤング率(相対値)が130〜160、好ましくは132〜160である。また、後述する評価法による非磁性下地層と磁気記録層とからなる塗膜の収縮率は7.5〜18%、好ましくは8.0〜17%、より好ましくは8.5〜16%である。 The non-magnetic according to the present invention is coated with a surface coating as a non-magnetic powder for a non-magnetic underlayer using an acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder containing iron as a main component as the magnetic particle powder. When the hematite particle powder for the underlayer is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 3500 Oe), preferably 71.6 to 278.5 kA / m (900 to 3500 Oe), square The ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.87 to 0.95, preferably 0.88 to 0.95, and the glossiness of the coating film is 207 to 300%, preferably 212 to 300%. The film surface roughness Ra is 6.3 nm or less, preferably 2.0 to 5.8 nm, and the Young's modulus (relative value) is 130 to 160, preferably 132 to 160. Further, the shrinkage ratio of the coating film composed of the nonmagnetic underlayer and the magnetic recording layer according to the evaluation method described later is 7.5 to 18%, preferably 8.0 to 17%, more preferably 8.5 to 16%. is there.
また、非磁性下地層用非磁性粉末として粒子内部にアルミニウムを含有させた本発明に係る非磁性下地層用ヘマタイト粒子粉末を用いた場合には、磁気記録媒体の耐久性が向上し、耐久性のうち走行耐久性は20分以上、好ましくは22分以上であり、すり傷特性はA又はB、好ましくはAである。 Further, when the nonmagnetic underlayer hematite particle powder according to the present invention containing aluminum inside the particle is used as the nonmagnetic underlayer nonmagnetic powder, the durability of the magnetic recording medium is improved and the durability is improved. Among them, the running durability is 20 minutes or more, preferably 22 minutes or more, and the scratch property is A or B, preferably A.
殊に、磁性粒子粉末として鉄を主成分とする針状金属磁性粒子粉末又は針状鉄合金磁性粒子粉末を用い、非磁性下地層用非磁性粉末として高純度化した本発明に係る非磁性下地層用ヘマタイト粒子粉末を用いた場合には、塗膜の保磁力値の変化率(%)で示す腐蝕性が10.0%以下、好ましくは9.5%以下、飽和磁化値の変化率(%)で示す腐蝕性が10.0%以下、好ましくは9.5%以下である。 In particular, a non-magnetic under magnetic powder according to the present invention is used as a non-magnetic powder for a non-magnetic underlayer using acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly composed of iron as the magnetic particle powder. When the hematite particle powder for the formation is used, the corrosivity shown by the change rate (%) of the coercive force value of the coating film is 10.0% or less, preferably 9.5% or less, and the change rate of the saturation magnetization value ( %) Is 10.0% or less, preferably 9.5% or less.
次に、本発明に係る磁気記録媒体の製造法について述べる。 Next, a method for manufacturing a magnetic recording medium according to the present invention will be described.
本発明に係る磁気記録媒体は、常法により、非磁性支持体上にヘマタイト粒子粉末、結合剤樹脂及び溶剤を含む非磁性塗料を塗布、乾燥して非磁性下地層を形成し、該非磁性下地層上に磁性粒子粉末、結合剤樹脂及び溶剤を含む磁性塗料を塗布して塗膜を形成した後、磁場配向し、次いで、カレンダー処理をした後、硬化させることにより得ることができる。 In the magnetic recording medium according to the present invention, a nonmagnetic undercoat layer is formed by applying a nonmagnetic coating material containing a hematite particle powder, a binder resin and a solvent onto a nonmagnetic support by a conventional method, and drying the nonmagnetic underlayer. It can be obtained by applying a magnetic coating material containing magnetic particle powder, binder resin and solvent on the base layer to form a coating film, orienting in a magnetic field, then calendering and curing.
前記非磁性下地層及び前記磁気記録層の形成に用いる溶剤としては、磁気記録媒体に汎用されているメチルエチルケトン、トルエン、シクロヘキサノン、メチルイソブチルケトン、テトラヒドロフラン及びその混合物等を使用することができる。 As the solvent used for forming the non-magnetic underlayer and the magnetic recording layer, methyl ethyl ketone, toluene, cyclohexanone, methyl isobutyl ketone, tetrahydrofuran and a mixture thereof, which are widely used for magnetic recording media, can be used.
溶剤の使用量は、ヘマタイト粒子粉末又は磁性粒子粉末100重量部に対してその総量で50〜1000重量部である。50重量部未満では塗料とした場合に粘度が高くなりすぎ塗布が困難となる。1000重量部を超える場合には、塗膜を形成する際の溶剤の揮発量が多くなりすぎ工業的に不利となる。 The usage-amount of a solvent is 50-1000 weight part in the total amount with respect to 100 weight part of hematite particle powder or magnetic particle powder. If it is less than 50 parts by weight, the viscosity becomes too high when applied as a paint, making application difficult. When it exceeds 1000 parts by weight, the volatilization amount of the solvent when forming the coating film becomes too large, which is industrially disadvantageous.
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本発明において最も重要な点は、本発明に係るヘマタイト粒子粉末は分散性及び充填性に優れており、該ヘマタイト粒子粉末を用いた非磁性下地層を有する磁気記録媒体は表面平滑性に優れるという点である。
<Action>
The most important point in the present invention is that the hematite particle powder according to the present invention is excellent in dispersibility and filling properties, and the magnetic recording medium having a nonmagnetic underlayer using the hematite particle powder is excellent in surface smoothness. Is a point.
本発明に係るヘマタイト粒子粉末の分散性及び充填性が優れている理由について、本発明者は次のように考えている。 The present inventor considers the reason why the dispersibility and filling property of the hematite particle powder according to the present invention are excellent as follows.
一般に、粒子形状が針状である場合には、ビヒクル中での粒子の絡み合いが起こりやすく、所望の分散性を得ることが困難であるが、本発明に係る非磁性下地層用ヘマタイト粒子粉末は、紡錘状ゲータイト粒子を摩砕処理することによって紡錘状ゲータイトの粒子端を開いた状態とし、当該粒子形態を崩さない温度範囲で加熱処理してヘマタイト粒子粉末にしたことにより、紡錘状であって、しかも、粒子端が開いたヘマタイト粒子となっているため、針状粒子に比べてビヒクル中における分散が容易となり、その結果、充填性も向上したものと考えている。 In general, when the particle shape is needle-like, the particles are easily entangled in the vehicle, and it is difficult to obtain a desired dispersibility. The spindle-shaped goethite particles are milled to make the spindle-shaped goethite particles open, and heat-treated in a temperature range that does not destroy the particle morphology to form hematite particles. In addition, since the particles are hematite particles having an open end, it is easier to disperse in the vehicle than the acicular particles, and as a result, it is considered that the filling property is improved.
更に、本発明に係る非磁性下地層用ヘマタイト粒子粉末を用いた非磁性下地層を有する磁気記録媒体の表面平滑性が優れている理由について、本発明者は、本発明に係るヘマタイト粒子粉末は、前述のように粒子端が開いた粒子形態を有しているのでカレンダー処理による圧縮が掛かり易く、表面平滑性向上効果が得られ易いためと推定している。 Further, for the reason why the surface smoothness of the magnetic recording medium having a nonmagnetic underlayer using the nonmagnetic underlayer hematite particle powder according to the present invention is excellent, the present inventor As described above, it is presumed that since the particle shape is such that the particle ends are open, the compression by the calendar process is easily applied, and the effect of improving the surface smoothness is easily obtained.
本発明の代表的な実施の形態は、次の通りである。 A typical embodiment of the present invention is as follows.
ヘマタイト粒子、紡錘状ゲータイト粒子及び磁性粒子の平均長軸径、平均短軸径又は平均板面径、平均厚みは、電子顕微鏡写真を縦方向及び横方向にそれぞれ4倍に拡大した写真に示される粒子約350個について長軸径、短軸径をそれぞれ測定し、その平均値で示した。 The average major axis diameter, average minor axis diameter or average plate surface diameter, and average thickness of hematite particles, spindle-shaped goethite particles, and magnetic particles are shown in photographs obtained by enlarging the electron micrographs four times in the vertical and horizontal directions, respectively. The major axis diameter and minor axis diameter of each of about 350 particles were measured and indicated by the average value.
また、ヘマタイト粒子の短軸径(W)と該ヘマタイト粒子の粒子端から長軸径の1/10の点(b)の粒子幅(Wb)との比は、上記電子顕微鏡写真から、同様にして、ヘマタイト粒子の粒子端から長軸径の1/10の点(b)における粒子幅(Wb)を測定し、短軸径(W)とヘマタイト粒子の粒子端から長軸径の1/10の点(b)における粒子幅(Wb)との比(W/Wb)の平均値で示した。 Further, the ratio between the minor axis diameter (W) of the hematite particles and the particle width (Wb) of the point (b) that is 1/10 of the major axis diameter from the particle end of the hematite particles is similarly determined from the above electron micrograph. Then, the particle width (Wb) at the point (b) of 1/10 of the major axis diameter from the particle end of the hematite particle is measured, and the minor axis diameter (W) and 1/10 of the major axis diameter from the particle end of the hematite particle are measured. The average value of the ratio (W / Wb) to the particle width (Wb) at point (b).
軸比は、前記平均長軸径と前記平均短軸径との比で、板状比は、平均板面径と平均厚みとの比で示した。 The axial ratio is the ratio between the average major axis diameter and the average minor axis diameter, and the plate ratio is the ratio between the average plate surface diameter and the average thickness.
比表面積値はBET法により測定した値で示した。 The specific surface area value was indicated by a value measured by the BET method.
ヘマタイト粒子粉末のシクロヘキサノンの吸液量は、試料1.0gを共栓付き丸底フラスコに入れ、ビューレットよりシクロヘキサノンを少量ずつ滴下し、丸底フラスコを振ってシクロヘキサノンを試料に吸液させる。試料が塊状となり吸液しなくなった時点の滴下シクロヘキサノン量を吸液量とする。 The amount of cyclohexanone absorbed in the hematite particle powder is as follows: 1.0 g of a sample is placed in a round bottom flask with a stopper, cyclohexanone is added dropwise from a burette, and the round bottom flask is shaken to absorb cyclohexanone into the sample. The amount of cyclohexanone dropped when the sample becomes agglomerated and no longer absorbs is taken as the amount of absorption.
ヘマタイト粒子粉末及び磁性粒子粉末の粒子内部や粒子表面に存在するAl量、Si量及び焼結防止剤のSi量及びP量のそれぞれは「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 amounts of Al, Si, and Si in the anti-sintering agent and P in the hematite particle powder and magnetic particle powder are “X-ray fluorescence analyzer 3063M type” (Rigaku Denki Kogyo Co., Ltd.) And manufactured according to JIS K0119 “General Rules for Fluorescence X-ray Analysis”.
粉体pH値は、試料5gを300mlの三角フラスコに秤り取り、煮沸した純水100mlを加え、加熱して煮沸状態を約5分間保持した後、栓をして常温まで放冷し、減量に相当する水を加えて再び栓をして1分間振り混ぜ、5分間静置した後、得られた上澄み液のpHをJIS Z 8802−7に従って測定し、得られた値を粉体pH値とした。 The pH value of the powder was measured by weighing 5 g of a sample into a 300 ml Erlenmeyer flask, adding 100 ml of boiled pure water, heating and holding the boiled state for about 5 minutes, then plugging it and letting it cool to room temperature. After adding water corresponding to the above, stoppered again, shaken for 1 minute, allowed to stand for 5 minutes, and then measured the pH of the obtained supernatant according to JIS Z 8802-7. It was.
可溶性ナトリウム塩の含有量及び可溶性硫酸塩の含有量は、上記粉体pH値の測定用に作製した上澄み液をNo.5Cの濾紙を用いて濾過し、濾液中のNa+及びSO4 2−を誘導結合プラズマ発光分光分析装置(セイコー電子工業株式会社製)を用いて測定した。 The content of the soluble sodium salt and the content of the soluble sulfate were determined by changing the supernatant prepared for measurement of the powder pH value as No. Filtration was performed using 5C filter paper, and Na + and SO 4 2− in the filtrate were measured using an inductively coupled plasma emission spectrometer (manufactured by Seiko Denshi Kogyo Co., Ltd.).
塗料粘度は、得られた塗料の25℃における塗料粘度を、E型粘度計EMD−R(株式会社東京計器製)を用いて測定し、ずり速度D=1.92sec−1における値で示した。 The coating viscosity at 25 ° C. of the obtained coating was measured using an E-type viscometer EMD-R (manufactured by Tokyo Keiki Co., Ltd.) and indicated by a value at a shear rate D = 1.92 sec −1 . .
非磁性下地層及び磁気記録層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)を用いて塗膜の45°光沢度を測定して求めた。 The glossiness of the coating surface of the nonmagnetic underlayer and magnetic recording layer was determined by measuring the 45 ° glossiness of the coating using “Gloss Meter UGV-5D” (manufactured by Suga Test Instruments Co., Ltd.).
非磁性下地層及び磁気記録層の塗膜の表面粗度Raは、「Surfcom−575A」(東京精密株式会社製)を用いて塗布膜の中心線平均粗さを測定した。 The surface roughness Ra of the coating film of the nonmagnetic underlayer and the magnetic recording layer was determined by measuring the centerline average roughness of the coating film using “Surfcom-575A” (manufactured by Tokyo Seimitsu Co., Ltd.).
非磁性下地層及び磁気記録層の塗膜の強度は、「オートグラフ」(株式会社島津製作所製)を用いて塗膜のヤング率を測定し、市販ビデオテープ「AV T−120(日本ビクター株式会社製)」のヤング率との相対値で表した。相対値が高いほど塗膜の強度が良好であることを示す。 The coating strength of the nonmagnetic underlayer and magnetic recording layer was measured by measuring the Young's modulus of the coating using “Autograph” (manufactured by Shimadzu Corporation), and the commercially available video tape “AV T-120 (Nippon Victor Co., Ltd.). It was expressed as a relative value with the Young's modulus of “made by the company”. It shows that the intensity | strength of a coating film is so favorable that a relative value is high.
磁気記録媒体を構成する非磁性支持体、非磁性下地層及び磁気記録層の各層の厚みは、次の通りの測定手法によって測定した。 The thickness of each layer of the nonmagnetic support, the nonmagnetic underlayer and the magnetic recording layer constituting the magnetic recording medium was measured by the following measurement method.
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、先ず、非磁性支持体の膜厚(A)を測定する。次に、非磁性支持体と該非磁性支持体上に形成された非磁性下地層との厚み(B)(非磁性支持体の厚みと非磁性下地層の厚みとの総和)を同様にして測定する。更に、非磁性下地層上に磁気記録層を形成することにより得られた磁気記録媒体の厚み(C)(非磁性支持体の厚みと非磁性下地層の厚みと磁気記録層の厚みとの総和)を同様にして測定する。そして、非磁性下地層の厚みは(B)−(A)で示し、磁気記録層の厚みは(C)−(B)で示した。 First, the film thickness (A) of the nonmagnetic support is measured using a digital electronic micrometer K351C (manufactured by Anritsu Electric Co., Ltd.). Next, the thickness (B) of the nonmagnetic support and the nonmagnetic underlayer formed on the nonmagnetic support (the sum of the thickness of the nonmagnetic support and the nonmagnetic underlayer) was measured in the same manner. To do. Further, the thickness (C) of the magnetic recording medium obtained by forming the magnetic recording layer on the nonmagnetic underlayer (the sum of the thickness of the nonmagnetic support, the thickness of the nonmagnetic underlayer, and the thickness of the magnetic recording layer). ) Is measured in the same manner. The thickness of the nonmagnetic underlayer is indicated by (B)-(A), and the thickness of the magnetic recording layer is indicated by (C)-(B).
非磁性下地層の塗膜の収縮率は、下記測定方法によって測定した。 The shrinkage ratio of the coating film of the nonmagnetic underlayer was measured by the following measuring method.
(1)ヘマタイト粒子粉末12gと結合剤樹脂溶液(スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂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混合して混合物(固形分率72%)を得、この混合物を更にプラストミルで30分間混練して混練物を得た。
(2)前記混練物を1.5mmφガラスビーズ95g、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とともに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を得た。
ヘマタイト粒子粉末 100.0重量部、
スルホン酸ナトリウム基を有する
塩化ビニル−酢酸ビニル共重合樹脂 10.0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 10.0重量部、
シクロヘキサノン 44.6重量部、
メチルエチルケトン 111.4重量部、
トルエン 66.9重量部。
(3)次に、得られた非磁性塗料を非磁性支持体上にアプリケーターを用いて55μmの厚さに塗布し、乾燥させて非磁性下地層を形成した。
(4)塗布後の乾燥させた塗膜を85℃、200kg/cmで4回カレンダー処理を行い、該塗膜のカレンダー処理前の膜厚t0(μm)とカレンダー処理後の膜厚t1(μm)とから下記式に従って非磁性下地層の塗膜の収縮率(%)を求めた。
塗膜の収縮率(%)={(t0−t1)/t0}×100
t0:カレンダー前の非磁性下地層の厚み(μm)
t1:カレンダー後の非磁性下地層の厚み(μm)
(1) 12 g of hematite particle powder, binder resin solution (vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 30% by weight and cyclohexanone 70% by weight) and cyclohexanone are mixed to obtain a mixture (solid content ratio 72% This mixture was further kneaded with a plastmill for 30 minutes to obtain a kneaded product.
(2) The kneaded product is 95 g of 1.5 mmφ glass beads, an additional binder resin solution (polyurethane resin having a sodium sulfonate group 30 wt%, solvent (methyl ethyl ketone: toluene = 1: 1) 70 wt%), cyclohexanone, It was added to a 140 ml glass bottle together with methyl ethyl ketone and toluene, and mixed and dispersed for 6 hours with a paint shaker to obtain a nonmagnetic paint.
100.0 parts by weight of hematite particle powder,
Has sodium sulfonate group
10.0 parts by weight of vinyl chloride-vinyl acetate copolymer resin,
10.0 parts by weight of a polyurethane resin having a sodium sulfonate group,
44.6 parts by weight of cyclohexanone,
111.4 parts by weight of methyl ethyl ketone,
66.9 parts by weight of toluene.
(3) Next, the obtained nonmagnetic coating material was applied on a nonmagnetic support to a thickness of 55 μm using an applicator and dried to form a nonmagnetic underlayer.
(4) The dried coating film after coating is calendered four times at 85 ° C. and 200 kg / cm, and the film thickness t 0 (μm) of the coating film before calendar processing and the film thickness t 1 after calendar processing. From (μm), the shrinkage rate (%) of the coating film of the nonmagnetic underlayer was determined according to the following formula.
Shrinkage rate of coating film (%) = {(t 0 −t 1 ) / t 0 } × 100
t 0 : thickness of nonmagnetic underlayer before calendar (μm)
t 1 : thickness of nonmagnetic underlayer after calendar (μm)
非磁性下地層と磁気記録層からなる塗膜の収縮率は、下記測定方法によって測定した。 The shrinkage ratio of the coating film composed of the nonmagnetic underlayer and the magnetic recording layer was measured by the following measuring method.
(1)ヘマタイト粒子粉末12gと結合剤樹脂溶液(スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂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混合して混合物(固形分率72%)を得、この混合物を更にプラストミルで30分間混練して混練物を得た。
(2)前記混練物を1.5mmφガラスビーズ95g、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とともに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を得た。
ヘマタイト粒子粉末 100.0重量部、
スルホン酸ナトリウム基を有する
塩化ビニル−酢酸ビニル共重合樹脂 10.0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 10.0重量部、
シクロヘキサノン 44.6重量部、
メチルエチルケトン 111.4重量部、
トルエン 66.9重量部。
(3)次に、得られた非磁性塗料を非磁性支持体上にアプリケーターを用いて55μmの厚さに塗布し、乾燥させて非磁性下地層を形成した。
(4)磁性粒子粉末12g、研磨剤(アルミナ)1.2g、カーボンブラック微粒子粉末0.12g、結合剤樹脂溶液(スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂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混合して混合物(固形分率78%)を得、この混合物を更にプラストミルで30分間混練して混練物を得た。
(5)この混練物を1.5mmφガラスビーズ95g、追加結合剤樹脂溶液(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とともに140mlガラス瓶に添加し、ペイントシェーカーで6時間混合・分散を行って磁性塗料を得た。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。
磁性粒子粉末 100.0重量部
スルホン酸ナトリウム基を有する
塩化ビニル−酢酸ビニル共重合樹脂 10.0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 10.0重量部
研磨剤(アルミナ) 10.0重量部
カーボンブラック微粒子粉末 1.0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 65.8重量部
メチルエチルケトン 164.5重量部
トルエン 98.7重量部
(6)得られた磁性塗料を、上述の非磁性下地層を有する基体の上にアプリケーターを用いて15μmの厚さに塗布した後、磁場中において配向・乾燥した。
(7)塗布後の乾燥させた塗膜を85℃、200kg/cmで4回カレンダー処理を行い、該塗膜のカレンダー処理前の膜厚t2(μm)とカレンダー処理後の膜厚t3(μm)とから下記式に従って塗膜の収縮率(%)を求める。
塗膜の収縮率(%)={(t2−t3)/t2}×100
t2:カレンダー前の非磁性下地層の厚みと磁気記録層の厚みとの合計(μm)
t3:カレンダー後の非磁性下地層の厚みと磁気記録層の厚みとの合計(μm)
(1) 12 g of hematite particle powder, binder resin solution (vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 30% by weight and cyclohexanone 70% by weight) and cyclohexanone are mixed to obtain a mixture (solid content ratio 72% This mixture was further kneaded with a plastmill for 30 minutes to obtain a kneaded product.
(2) The kneaded product is 95 g of 1.5 mmφ glass beads, an additional binder resin solution (polyurethane resin having a sodium sulfonate group 30 wt%, solvent (methyl ethyl ketone: toluene = 1: 1) 70 wt%), cyclohexanone, It was added to a 140 ml glass bottle together with methyl ethyl ketone and toluene, and mixed and dispersed for 6 hours with a paint shaker to obtain a nonmagnetic paint.
100.0 parts by weight of hematite particle powder,
Has sodium sulfonate group
10.0 parts by weight of vinyl chloride-vinyl acetate copolymer resin,
10.0 parts by weight of a polyurethane resin having a sodium sulfonate group,
44.6 parts by weight of cyclohexanone,
111.4 parts by weight of methyl ethyl ketone,
66.9 parts by weight of toluene.
(3) Next, the obtained nonmagnetic coating material was applied on a nonmagnetic support to a thickness of 55 μm using an applicator and dried to form a nonmagnetic underlayer.
(4) Magnetic particle powder 12 g, abrasive (alumina) 1.2 g, carbon black fine particle powder 0.12 g, binder resin solution (vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 30% by weight and cyclohexanone 70 % By weight) and cyclohexanone were mixed to obtain a mixture (solid content ratio 78%), and this mixture was further kneaded with a plast mill for 30 minutes to obtain a kneaded product.
(5) 95 g of 1.5 mmφ glass beads, additional binder resin solution (30% by weight of polyurethane resin having sodium sulfonate group, 70% by weight of solvent (methyl ethyl ketone: toluene = 1: 1)), cyclohexanone, methyl ethyl ketone And it added to a 140 ml glass bottle with toluene, and mixed and disperse | distributed for 6 hours with the paint shaker, and obtained the magnetic coating material. Then, a lubricant and a curing agent were added, and further mixed and dispersed for 15 minutes with a paint shaker.
Magnetic particle powder 100.0 parts by weight Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 10.0 parts by weight Polyurethane resin having sodium sulfonate group 10.0 parts by weight Polishing agent (alumina) 10.0 parts by weight Carbon black fine particle powder 1.0 part by weight Lubricant (myristic acid: butyl stearate = 1: 2) 3.0 part by weight Curing agent (polyisocyanate) 5.0 part by weight Cyclohexanone 65.8 part by weight Methyl ethyl ketone 164.5 part by weight Part 98.7 parts by weight of toluene (6) The obtained magnetic coating material was applied on a substrate having the above-mentioned nonmagnetic underlayer to a thickness of 15 μm using an applicator, and then oriented and dried in a magnetic field.
(7) The dried coating film after application is calendered four times at 85 ° C. and 200 kg / cm, and the film thickness t 2 (μm) before the calendering process and the film thickness t 3 after the calendering process. From (μm), the shrinkage ratio (%) of the coating film is determined according to the following formula.
Shrinkage rate of coating film (%) = {(t 2 −t 3 ) / t 2 } × 100
t 2 : Sum of the thickness of the nonmagnetic underlayer before the calendar and the thickness of the magnetic recording layer (μm)
t 3 : Sum of the thickness of the nonmagnetic underlayer after the calendar and the thickness of the magnetic recording layer (μm)
磁性粒子粉末及び磁気記録媒体の磁気特性は、「振動試料型磁力計VSM−3S−15」(東英工業株式会社製)を使用し、外部磁場795.8kA/m(10kOe)までかけて測定した。 The magnetic properties of the magnetic particle powder and the magnetic recording medium were measured using an “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Kogyo Co., Ltd.) up to an external magnetic field of 795.8 kA / m (10 kOe). did.
磁気記録媒体の走行耐久性は、「Media Durability Tester MDT−3000」(Steinberg Associates社製)を用いて、負荷1.96N(200gw)、ヘッドとテープとの相対速度16m/sにおける実可動時間で評価した。実可動時間が長いほど走行耐久性が良いことを示す。 The running durability of the magnetic recording medium was measured by using “Media Duability Tester MDT-3000” (manufactured by Steinberg Associates) with a load of 1.96 N (200 gw) and an actual moving time at a relative speed of 16 m / s between the head and the tape. evaluated. The longer the actual movable time, the better the running durability.
すり傷特性は、走行後のテープの表面を顕微鏡で観察し、すり傷の有無を目視で評価し、下記の4段階の評価を行った。 For the scratch characteristics, the surface of the tape after running was observed with a microscope, the presence or absence of the scratch was visually evaluated, and the following four grades were evaluated.
A:すり傷なし
B:すり傷若干有り
C:すり傷有り
D:ひどいすり傷有り
A: No scratch B: Slight scratch C: Scratch D: Severe scratch
磁気記録層中の鉄を主成分とする金属磁性粒子粉末の腐蝕に伴う磁気記録媒体の磁気特性の経時変化は、磁気記録媒体を温度60℃、相対湿度90%の環境下に14日間放置し、放置前後の保磁力値及び飽和磁束密度値を測定し、その変化量を放置前の値で除した値を変化率として百分率で示した。 The change over time in the magnetic properties of the magnetic recording medium accompanying the corrosion of the metal magnetic particle powder containing iron as a main component in the magnetic recording layer is that the magnetic recording medium is left in an environment of a temperature of 60 ° C. and a relative humidity of 90% for 14 days. The coercive force value and saturation magnetic flux density value before and after standing were measured, and the value obtained by dividing the amount of change by the value before standing was expressed as a percentage.
<実施の形態1>
<ヘマタイト粒子粉末の製造>
紡錘状ゲータイト粒子の湿ケーキを水中に分散させることによって得られる紡錘状ゲータイト粒子粉末(平均長軸径0.196μm、平均短軸径0.0261μm、軸比7.5、W/wb1.31、内部含有Al量1.35重量%)20kgを含む水懸濁液中に3号水ガラス1384g(紡錘状ゲータイト粒子粉末に対してSiO2換算で2.0重量%に相当する)を添加し、混合攪拌した後、濾別、水洗、乾燥して焼結防止処理を行った。
<Embodiment 1>
<Manufacture of hematite particle powder>
Spindle-shaped goethite particle powder obtained by dispersing a wet cake of spindle-shaped goethite particles in water (average major axis diameter 0.196 μm, average minor axis diameter 0.0261 μm, axial ratio 7.5, W / wb 1.31, 1384 g of No. 3 water glass (corresponding to 2.0 wt% in terms of SiO 2 with respect to the spindle-shaped goethite particle powder) is added to an aqueous suspension containing 20 kg of an Al content of 1.35 wt% inside, After mixing and stirring, the mixture was filtered, washed with water, and dried to prevent sintering.
次いで、この焼結防止処理を施した紡錘状ゲータイト粒子粉末を含むスラリーの濃度を100g/lに調製し、超微粒摩砕機「スーパーマスコロイダー」(製品名、増幸産業株式会社製)を用いて、軸回転数2000rpmにおいて5回パスさせて摩砕処理を行った後、濾別、水洗、乾燥した。 Next, the concentration of the slurry containing the spindle-shaped goethite particle powder subjected to the sintering prevention treatment is adjusted to 100 g / l, and an ultrafine grinding machine “Super Mass Colloid” (product name, manufactured by Masuko Sangyo Co., Ltd.) is used. After passing through 5 times at a shaft rotational speed of 2000 rpm, grinding was performed, followed by filtration, washing with water and drying.
得られた紡錘状ゲータイト粒子粉末を350℃で60分間加熱処理することにより、紡錘状ヘマタイト粒子粉末を得た。 The obtained spindle-shaped goethite particle powder was heat-treated at 350 ° C. for 60 minutes to obtain spindle-shaped hematite particle powder.
ここに得た紡錘状ヘマタイト粒子粉末の平均長軸径は0.168μm、平均短軸径は0.0280μm、軸比は6.0、W/Wb1.32、BET比表面積値は101.6m2/g、シクロヘキサノンの吸液量は0.85ml/g、Al含有量は1.48重量%、焼結防止剤はSiO2換算で1.95重量%であった。 The spindle-shaped hematite particles obtained here have an average major axis diameter of 0.168 μm, an average minor axis diameter of 0.0280 μm, an axial ratio of 6.0, W / Wb of 1.32, and a BET specific surface area value of 101.6 m 2. / G, the amount of cyclohexanone absorbed was 0.85 ml / g, the Al content was 1.48 wt%, and the sintering inhibitor was 1.95 wt% in terms of SiO 2 .
透過型電子顕微鏡(TEM)写真(×30,000)観察の結果、得られた紡錘状ヘマタイト粒子は、粒子の両方の粒子端が開いた状態であることが認められた。 As a result of observation with a transmission electron microscope (TEM) photograph (× 30,000), it was confirmed that the obtained spindle-shaped hematite particles were in a state where both ends of the particles were open.
<非磁性下地層の製造>
ここに得た紡錘状ヘマタイト粒子粉末12gと結合剤樹脂溶液(スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂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混合して混合物(固形分率72%)を得、この混合物を更にプラストミルで30分間混練して混練物を得た。
<Manufacture of nonmagnetic underlayer>
12 g of the spindle-shaped hematite particle powder obtained here, a binder resin solution (30% by weight of vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group and 70% by weight of cyclohexanone) and cyclohexanone were mixed to obtain a mixture (solid content The mixture was further kneaded with a plast mill for 30 minutes to obtain a kneaded product.
この混練物を1.5mmφガラスビーズ95g、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とともに140mlガラス瓶に添加し、ペイントシェーカーで6時間混合・分散を行って塗料組成物を得た。 This kneaded product was mixed with 95 g of 1.5 mmφ glass beads, an additional binder resin solution (polyurethane resin having a sodium sulfonate group 30 wt%, solvent (methyl ethyl ketone: toluene = 1: 1) 70 wt%), cyclohexanone, methyl ethyl ketone and toluene. The mixture was added to a 140 ml glass bottle and mixed and dispersed for 6 hours with a paint shaker to obtain a coating composition.
得られた非磁性塗料の組成は、下記の通りであった。 The composition of the obtained nonmagnetic coating material was as follows.
紡錘状ヘマタイト粒子粉末 100重量部、
スルホン酸ナトリウム基を有する
塩化ビニル−酢酸ビニル共重合樹脂 10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 10重量部、
シクロヘキサノン 44.6重量部、
メチルエチルケトン 111.4重量部、
トルエン 66.9重量部。
100 parts by weight of spindle-shaped hematite particle powder,
Has sodium sulfonate group
10 parts by weight of vinyl chloride-vinyl acetate copolymer resin,
10 parts by weight of a polyurethane resin having a sodium sulfonate group,
44.6 parts by weight of cyclohexanone,
111.4 parts by weight of methyl ethyl ketone,
66.9 parts by weight of toluene.
得られた非磁性塗料の塗料粘度は2,637cPであった。 The obtained nonmagnetic paint had a paint viscosity of 2,637 cP.
次に、得られた非磁性塗料を、厚さ12μmのポリエチレンテレフタレートフィルム上に、アプリケーターを用いて55μmの厚さに塗布し、乾燥させることにより非磁性下地層を形成した。 Next, the obtained nonmagnetic coating material was applied on a polyethylene terephthalate film having a thickness of 12 μm to a thickness of 55 μm using an applicator and dried to form a nonmagnetic underlayer.
得られた非磁性下地層の塗布厚みは3.50μm、光沢は216%、表面粗度Raは5.5nm、ヤング率(相対値)は135であった。カレンダー処理後の非磁性下地層の膜厚は3.05μmであり、非磁性下地層の塗膜の圧縮率は12.8%であった。 The coating thickness of the obtained nonmagnetic underlayer was 3.50 μm, the gloss was 216%, the surface roughness Ra was 5.5 nm, and the Young's modulus (relative value) was 135. The thickness of the nonmagnetic underlayer after the calendar treatment was 3.05 μm, and the compression ratio of the coating film of the nonmagnetic underlayer was 12.8%.
<磁気記録媒体の製造>
鉄を主成分とする針状金属磁性粉末(平均長軸径0.103μm、平均短軸径0.0155μm、軸比6.6、保磁力値181.9kA/m(2,286Oe)、飽和磁化値138Am2/kg(138emu/g))12g、カーボンブラック微粒子粉末0.36g及び研磨材としてアルミナ粒子粉末1.2g、結合剤樹脂溶液(スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂30重量%とシクロヘキサノン70重量%からなる)及びシクロヘキサノンとを混合し、固形分率78%において、プラストミルを用いて30分間混練して混練物を得た。
<Manufacture of magnetic recording media>
Acicular metal magnetic powder mainly composed of iron (average major axis diameter 0.103 μm, average minor axis diameter 0.0155 μm, axial ratio 6.6, coercive force 181.9 kA / m (2,286 Oe), saturation magnetization Value 138 Am 2 / kg (138 emu / g)) 12 g, carbon black fine particle powder 0.36 g and alumina particle powder 1.2 g as an abrasive, binder resin solution (vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group) 30% by weight and 70% by weight cyclohexanone) and cyclohexanone were mixed and kneaded at a solid content of 78% using a plastmill for 30 minutes to obtain a kneaded product.
この混練物を140mlガラス瓶に1.5mmφガラスビーズ95gと追加樹脂結合剤溶液(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%、トルエン35重量%、メチルエチルケトン35重量%からなる)及びシクロヘキサノン、トルエン、メチルエチルケトンを添加し、ペイントシェーカーで6時間、混合・分散を行った。その後、得られた塗料組成物に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・分散を行った。 This kneaded product is placed in a 140 ml glass bottle with 95 g of 1.5 mmφ glass beads and an additional resin binder solution (consisting of 30% by weight of polyurethane resin having a sodium sulfonate group, 35% by weight of toluene and 35% by weight of methyl ethyl ketone), and cyclohexanone, toluene, methyl ethyl ketone. Was added and mixed and dispersed in a paint shaker for 6 hours. Thereafter, a lubricant and a curing agent were added to the obtained coating composition, and further mixed and dispersed for 15 minutes with a paint shaker.
得られた磁性塗料の組成は以下の通りである。
鉄を主成分とする針状金属磁性粒子粉末 100.0重量部、
研磨剤(アルミナ粒子粉末) 10.0重量部、
カーボンブラック微粒子粉末 3.0重量部、
スルホン酸ナトリウム基を有する塩化ビニル−酢酸ビニル共重合樹脂
10.0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 10.0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 65.8重量部、
メチルエチルケトン 164.5重量部、
トルエン 98.7重量部。
The composition of the obtained magnetic paint is as follows.
100.0 parts by weight of acicular metal magnetic particle powder mainly composed of iron,
Abrasive (alumina particle powder) 10.0 parts by weight,
3.0 parts by weight of carbon black fine particle powder,
Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group
10.0 parts by weight,
10.0 parts by weight of a polyurethane resin having a sodium sulfonate group,
Lubricant (myristic acid: butyl stearate = 1: 2) 3.0 parts by weight,
Curing agent (polyisocyanate) 5.0 parts by weight,
65.8 parts by weight of cyclohexanone,
164.5 parts by weight of methyl ethyl ketone,
98.7 parts by weight of toluene.
得られた磁性塗料の塗料粘度は8,499cPであった。 The resulting magnetic paint had a paint viscosity of 8,499 cP.
得られた磁性塗料を、前記非磁性下地層を有する基体の上にアプリケーターを用いて15μmの厚さに塗布した後、磁場中において配向、乾燥した。このときの磁性層の厚みは1.01μm、塗布層の全厚は4.86μmであった。 The obtained magnetic paint was applied on a substrate having the nonmagnetic underlayer to a thickness of 15 μm using an applicator, and then oriented and dried in a magnetic field. At this time, the thickness of the magnetic layer was 1.01 μm, and the total thickness of the coating layer was 4.86 μm.
次いで、85℃、200kg/cmで4回カレンダー処理を行った後、60℃で24時間硬化反応を行い、1.27cm(0.5インチ)幅にスリットして磁気テープを得た。なお、カレンダー処理前後の塗膜の圧縮率は11.5%であった。得られた磁気テープの塗布層の全厚は4.30μm、保磁力値は185.6kA/m(2,332Oe)、角型比は0.90、光沢は236%、表面粗度Raは5.6nm、ヤング率(相対値)は136であり、耐久性のうち走行耐久性は30分以上、すり傷特性はAであった。 Next, after calendering four times at 85 ° C. and 200 kg / cm, a curing reaction was performed at 60 ° C. for 24 hours, and slitting to a width of 1.27 cm (0.5 inch) gave a magnetic tape. The compressibility of the coating film before and after the calendar treatment was 11.5%. The total thickness of the coated layer of the obtained magnetic tape was 4.30 μm, the coercive force value was 185.6 kA / m (2,332 Oe), the squareness ratio was 0.90, the gloss was 236%, and the surface roughness Ra was 5 1.6 nm, Young's modulus (relative value) was 136, running durability was 30 minutes or more, and scratch characteristics were A.
次に、前記実施の形態1に準じて製造した実施例並びに比較例を挙げる。 Next, examples and comparative examples manufactured according to the first embodiment will be given.
紡錘状ゲータイト粒子A、B及び針状ゲータイト粒子C:
紡錘状ゲータイト粒子粉末として、表1に示す特性を有する紡錘状ゲータイト粒子粉末及び針状ゲータイト粒子粉末を用意した。
Spindle-shaped goethite particles A and B and acicular goethite particles C:
As the spindle-shaped goethite particle powder, spindle-shaped goethite particle powder and needle-like goethite particle powder having the characteristics shown in Table 1 were prepared.
<摩砕処理>
実施例1及び2、比較例1〜4、参考例1:
ゲータイト粒子の種類、焼結防止処理における焼結防止剤の種類及び添加量、摩砕処理の有無、摩砕処理におけるスラリー濃度及び回転数、加熱処理における加熱温度及び時間を種々変化させた以外は前記発明の実施の形態と同様にして非磁性粒子粉末を得た。
<Milling process>
Examples 1 and 2, Comparative Examples 1 to 4, Reference Example 1:
Except for changing the type of goethite particles, the type and amount of the sintering inhibitor in the anti-sintering treatment, the presence or absence of the grinding treatment, the slurry concentration and rotation speed in the grinding treatment, and the heating temperature and time in the heat treatment. A nonmagnetic particle powder was obtained in the same manner as in the embodiment of the invention.
このときの製造条件を表2に、得られた紡錘状ヘマタイト粒子粉末の諸特性を表3に示す。 The production conditions at this time are shown in Table 2, and various properties of the obtained spindle-shaped hematite particle powder are shown in Table 3.
なお、比較例5はゲータイト粒子Aを摩砕処理することなく、340℃で加熱脱水処理した後、650℃で加熱処理したヘマタイト粒子粉末である。参考例1はゲータイト粒子Cを摩砕処理した後、340℃で加熱処理したヘマタイト粒子粉末である。 Comparative Example 5 is a hematite particle powder that is heat-dehydrated at 340 ° C. and then heat-treated at 650 ° C. without grinding the goethite particles A. Reference Example 1 is a hematite particle powder that is heat-treated at 340 ° C. after the goethite particles C are ground.
実施例1及び2で得られたヘマタイト粒子粉末は、透過型電子顕微鏡(TEM)写真観察の結果、粒子端が開いた形状を有していることが認められた。 As a result of observation with a transmission electron microscope (TEM), the hematite particle powders obtained in Examples 1 and 2 were found to have a shape with open ends.
一方、比較例1で得られたヘマタイト粒子粉末は、粒子端が閉じた形状を有していることが認められた。 On the other hand, it was confirmed that the hematite particle powder obtained in Comparative Example 1 had a shape in which the particle ends were closed.
<アルカリ水溶液中の加熱処理>
実施例3
実施例1で得られたヘマタイト粒子粉末600gを純水3.5lに投入し、ホモミキサー(特殊機化工業株式会社製)を用いて60分間解膠した。
<Heat treatment in alkaline aqueous solution>
Example 3
600 g of the hematite particle powder obtained in Example 1 was put into 3.5 l of pure water, and peptized for 60 minutes using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).
次に、得られたヘマタイト粒子粉末のスラリーを横型SGM(ディスパマットSL:エスシー・アディケム株式会社製)で循環しながら、軸回転数2000rpmのもとで3時間混合・分散した。得られたスラリー中のヘマタイト粒子粉末の325mesh(目開き44μm)における篩残分は0%であった。 Next, the slurry of the obtained hematite particle powder was mixed and dispersed for 3 hours at a shaft rotational speed of 2000 rpm while circulating through a horizontal SGM (Dispamat SL: manufactured by ESC Adchem). The sieve residue in the 325 mesh (aperture 44 μm) of the hematite particle powder in the obtained slurry was 0%.
得られたヘマタイト粒子粉末のスラリーの濃度を100g/lに調製した後、スラリーを5l分取した。このスラリーを攪拌しながら、6NのNaOH水溶液を加えてスラリーのpH値を13.5に調整した。次に、このスラリーを攪拌しながら加熱して95℃まで昇温し、その温度で180分保持した。 After the concentration of the resulting hematite particle powder slurry was adjusted to 100 g / l, 5 l of the slurry was taken. While stirring this slurry, 6N NaOH aqueous solution was added to adjust the pH value of the slurry to 13.5. Next, this slurry was heated with stirring to a temperature of 95 ° C. and held at that temperature for 180 minutes.
次に、このスラリーをデカンテーション法により水洗し、pH値が10.5のスラリーとした。正確を期すため、この時点でのスラリー濃度を確認したところ96g/lであった。 Next, this slurry was washed with water by a decantation method to obtain a slurry having a pH value of 10.5. To ensure accuracy, the slurry concentration at this point was confirmed to be 96 g / l.
次に、ブフナーロートを用いて濾別し、純水を通水して濾液の電導度が30μs以下になるまで水洗し、その後、常法によって乾燥させた後、粉砕して、高純度化ヘマタイト粒子粉末を得た。 Next, the solution is filtered using a Buchner funnel, and pure water is passed through, and the filtrate is washed with water until the electric conductivity of the filtrate is 30 μs or less. Particle powder was obtained.
このときの製造条件を表4に、得られたヘマタイト粒子粉末の諸特性を表5に示す。 The production conditions at this time are shown in Table 4, and various characteristics of the obtained hematite particle powder are shown in Table 5.
実施例4:
ヘマタイト粒子粉末の種類、アルカリ水溶液のpH値、加熱温度及び加熱時間を種々変化させた以外は、前記実施例3と同様にして高純度化ヘマタイト粒子粉末を得た。
Example 4:
A highly purified hematite particle powder was obtained in the same manner as in Example 3 except that the type of hematite particle powder, the pH value of the alkaline aqueous solution, the heating temperature and the heating time were variously changed.
このときの製造条件を表4に、得られたヘマタイト粒子粉末の諸特性を表5に示す。 The production conditions at this time are shown in Table 4, and various characteristics of the obtained hematite particle powder are shown in Table 5.
得られたヘマタイト粒子粉末の透過型電子顕微鏡(TEM)写真観察の結果、実施例3及び4で得られたヘマタイト粒子粉末は、アルカリ水溶液中の加熱処理後も、粒子端が開いた形状を有していることが認められた。 As a result of observation of a transmission electron microscope (TEM) photograph of the obtained hematite particle powder, the hematite particle powder obtained in Examples 3 and 4 has a shape in which the particle ends are open even after heat treatment in an alkaline aqueous solution. It was recognized that
<表面被覆処理>
実施例5:
実施例1のヘマタイト粒子粉末10kgと水75lとを用いて、ヘマタイト粒子粉末を含むスラリーを得た。得られたヘマタイト粒子粉末を含む再分散スラリーのpH値を、水酸化ナトリウム水溶液を用いて10.5に調整した後、該スラリーに水を加えスラリー濃度を98g/lに調整した。このスラリー75lを加熱して60℃とし、このスラリー中に1.0mol/lのアルミン酸ナトリウム溶液4083ml(ヘマタイト粒子粉末に対してAl換算で1.5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7.5に調整した。この状態で30分間保持した後、濾過、水洗、乾燥、粉砕して粒子表面がアルミニウムの水酸化物により被覆されているヘマタイト粒子粉末を得た。
<Surface coating treatment>
Example 5:
A slurry containing hematite particle powder was obtained using 10 kg of the hematite particle powder of Example 1 and 75 l of water. The pH value of the redispersed slurry containing the obtained hematite particle powder was adjusted to 10.5 using an aqueous sodium hydroxide solution, and water was added to the slurry to adjust the slurry concentration to 98 g / l. 75 l of this slurry was heated to 60 ° C., and 4083 ml of 1.0 mol / l sodium aluminate solution (corresponding to 1.5% by weight in terms of Al with respect to the hematite particle powder) was added to this slurry, and 30 minutes After holding, the pH value was adjusted to 7.5 using acetic acid. After maintaining for 30 minutes in this state, filtration, washing, drying and pulverization were performed to obtain a hematite particle powder whose particle surface is coated with an aluminum hydroxide.
このときの製造条件を表6に、得られた表面処理済みヘマタイト粒子粉末の諸特性を表7に示す。 The production conditions at this time are shown in Table 6, and the properties of the obtained surface-treated hematite particles are shown in Table 7.
実施例6〜8:
実施例2〜4の各ヘマタイト粒子粉末を用い、表面被覆物の種類及び量を種々変化させた以外は、前記実施例5と同様にして粒子表面が被覆物で被覆されている非磁性粒子粉末を得た。
Examples 6-8:
The nonmagnetic particle powder in which the particle surface is coated with a coating in the same manner as in Example 5 except that each hematite particle powder of Examples 2 to 4 is used and the type and amount of the surface coating are variously changed. Got.
このときの製造条件を表6に、得られた表面処理済ヘマタイト粒子粉末の諸特性を表7に示す。 Table 6 shows the production conditions at this time, and Table 7 shows the characteristics of the obtained surface-treated hematite particle powder.
尚、表6の被覆物の種類は、Aがアルミニウムの水酸化物、Sがケイ素の酸化物であることを示す。 The types of coatings shown in Table 6 indicate that A is a hydroxide of aluminum and S is an oxide of silicon.
得られたヘマタイト粒子粉末の透過型電子顕微鏡(TEM)写真(×30,000)観察の結果、実施例5〜8で得られた各ヘマタイト粒子粉末は、表面被覆処理後も粒子端が開いた形状を有していることが認められた。 As a result of observation of a transmission electron microscope (TEM) photograph (× 30,000) of the obtained hematite particle powder, each hematite particle powder obtained in Examples 5 to 8 was opened at the particle end even after the surface coating treatment. It was found to have a shape.
<非磁性下地層の製造>
実施例9〜16、比較例5〜9、参考例2:
非磁性粒子粉末の種類を種々変化させた以外は、前記発明の実施の形態と同様にして非磁性下地層を得た。
<Manufacture of nonmagnetic underlayer>
Examples 9 to 16, Comparative Examples 5 to 9, Reference Example 2:
A nonmagnetic underlayer was obtained in the same manner as in the above embodiment except that the kind of nonmagnetic particle powder was variously changed.
このときの製造条件及び得られた非磁性下地層の諸特性を表8に示す。 Table 8 shows the manufacturing conditions and the characteristics of the obtained nonmagnetic underlayer.
磁性粒子粉末(1)〜(4):
磁性粒子粉末として表9に示す特性を有する磁性粒子粉末(1)〜(4)を用いた。
Magnetic particle powders (1) to (4):
Magnetic particle powders (1) to (4) having the characteristics shown in Table 9 were used as the magnetic particle powder.
<磁気記録媒体の製造>
実施例17〜24、比較例10〜14、参考例3:
非磁性下地層の種類及び磁性粒子の種類を種々変化させた以外は、前記発明の実施の形態と同様にして磁気記録媒体を得た。
<Manufacture of magnetic recording media>
Examples 17-24, Comparative Examples 10-14, Reference Example 3:
A magnetic recording medium was obtained in the same manner as in the above embodiment except that the type of the nonmagnetic underlayer and the type of the magnetic particles were variously changed.
このときの製造条件及び得られた磁気記録媒体の諸特性を表10及び表11に示す。 Tables 10 and 11 show the manufacturing conditions and the characteristics of the obtained magnetic recording medium.
Claims (6)
6. The magnetic recording medium according to claim 5, wherein a spindle-shaped metal magnetic particle powder mainly composed of iron having an axial ratio of 7.0 or less is used as the magnetic particle powder.
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