JP4143831B2 - Method for manufacturing magnetic recording medium - Google Patents

Description

【００５０】
（実施例２）
表１に示したように、第１の研磨テープとして、日本ミクロコーティング製研磨テープＧＣ３０００（研磨剤ＳｉＯ₂ ：研磨剤サイズ３０００メッシュ：モース硬度６）を用いた表面処理を２回行い、第２の研磨テープとして、日本ミクロコーティング製研磨テープＤ１００００（研磨剤ダイヤモンド：研磨剤サイズ１００００メッシュ：モース硬度１０：べナールセル現象により形成された凹条部有）を用いた表面処理を１回行ったことを除き、実施例１と同様にして磁気記録媒体を作製した。
【００５１】
（実施例３）
表１に示したように、第１の研磨テープとして、日本ミクロコーティング製研磨テープＧＣ４０００（研磨剤ＳｉＯ₂ ：研磨剤サイズ４０００メッシュ：モース硬度６）を用いた表面処理を３回行い、第２の研磨テープとして、日本ミクロコーティング製研磨テープＷＡ８０００（研磨剤Ａｌ₂ Ｏ₃ ：研磨剤サイズ８０００メッシュ：モース硬度９：べナールセル現象により形成された凹条部有）を用いた表面処理を２回行ったことを除き、実施例１と同様にして磁気記録媒体を作製した。
【００５２】
（実施例４）
表１に示したように、第１の研磨テープとして、日本ミクロコーティング製研磨テープＷＡ２０００（研磨剤Ａｌ₂ Ｏ₃ ：研磨剤サイズ２０００メッシュ：モース硬度９）を用いた表面処理を１回行い、第２の研磨テープとして、日本ミクロコーティング製研磨テープＤ８０００（研磨剤ダイヤモンド：研磨剤サイズ８０００メッシュ：モース硬度１０：べナールセル現象により形成された凹条部有）を用いた表面処理を１回行ったことを除き、実施例１と同様にして磁気記録媒体を作製した。
【００５３】
（実施例５）
表１に示したように、第１の研磨テープとして、日本ミクロコーティング製研磨テープＷＡ３０００（研磨剤Ａｌ₂ Ｏ₃ ：研磨剤サイズ３０００メッシュ：モース硬度９）を用いたことを除き、実施例１と同様にして磁気記録媒体を作製した。
【００５４】
（比較例１）
比較例１として、表１に示したように、第１の研磨テープに、日本ミクロコーティング製研磨テープＧＣ６０００（研磨剤ＳｉＯ₂ ：研磨剤サイズ６０００メッシュ：モース硬度６）を用いたことを除き、実施例１と同様にして磁気記録媒体を作製した。すなわち、実施例１よりも第１の研磨テープにおける研磨剤の大きさを小さくした。
【００５５】
（比較例２）
比較例２として、表１に示したように、第１の研磨テープに、日本ミクロコーティング製研磨テープＤ３０００（研磨剤ダイヤモンド：研磨剤サイズ３０００メッシュ：モース硬度１０）を用いたことを除き、実施例２と同様にして磁気記録媒体を作製した。すなわち、実施例２よりも第１の研磨テープにおける研磨剤のモース硬度を大きくし、磁性層１３に含まれる研磨剤のモース硬度９よりも大きくした。
【００５６】
（比較例３）
比較例３として、表１に示したように、第２の研磨テープに、日本ミクロコーティング製研磨テープＷＡ６０００（研磨剤Ａｌ₂ Ｏ₃ ：研磨剤サイズ６０００メッシュ：モース硬度９：凹条部無）を用いたことを除き、実施例３と同様にして磁気記録媒体を作製した。すなわち、実施例３よりも第１の研磨テープにおける研磨剤の大きさを大きくし、かつ凹条部をなくした。
【００５７】
（比較例４）
比較例４として、表１に示したように、第２の研磨テープに、日本ミクロコーティング製研磨テープＫ８０００（研磨剤Ｃｒ₂ Ｏ₃ ：研磨剤サイズ８０００メッシュ：モース硬度８：べナールセル現象により形成された凹条部有）を用いたことを除き、実施例４と同様にして磁気記録媒体を作製した。すなわち、実施例４よりも第２の研磨テープにおける研磨剤のモース硬度を小さくし、磁性層１３に含まれる研磨剤のモース硬度９よりも小さくした。
【００５８】
（比較例５）
比較例５として、表１に示したように、第１の研磨テープに、日本ミクロコーティング製研磨テープＷＡ１０００（研磨剤Ａｌ₂ Ｏ₃ ：研磨剤サイズ１０００メッシュ：モース硬度９）を用いたことを除き、実施例５と同様にして磁気記録媒体を作製した。すなわち、実施例５よりも第１の研磨テープにおける研磨剤の大きさを大きくした。
【００５９】
（評価）
得られた実施例１〜５および比較例１〜５の磁気記録媒体について、磁性層の表面の結合剤成分量を計測した。その結果を表２に示す。磁性層の表面の結合材成分量は、磁気記録媒体の表面から１０ｎｍまでの情報を得ることができる分析方法であるＸ線光電子分光分析（ＥＳＣＡ；Electron Spectroscopy for Chemical Analysis ）により、Ｃｌ−２ｐスペクトルとＦｅ−２ｐ（３／２）スペクトルとの積分強度比、および、Ｃ−１ＳスペクトルとＦｅ−２ｐ（３／２）スペクトルとの積分強度比として測定した。
【００６０】
【表２】

【００６１】
なお、ＥＳＣＡ測定の具体的な条件の一例としては、Ｘ線強度：８ｋＶ−２００Ｗ、Ｘ線アノード種類：モノクロメータＡｌ、測定Ｘ線：ＡｌＫα線、測定時間：１０分以内を挙げることができる。このような測定に使用する具体的な装置としては、アルバック・ファイ社製のＥＳＣＡ３２００型を使用することができる。
【００６２】
また、スリットされた磁気記録媒体を、カセットに組み込み、信頼性およびドロップアウト特性を測定した。その結果も表２に併せて示す。ここで「信頼性」とは、バージンテープを記録１パスおよび再生１パスさせる操作を、次々とかけ換えて行い、ヘッドクロッグが生じるまでの時間により測定した。表２には、ヘッドクロッグが生じるまでの時間が４０ｈ以上であった場合を良、４０ｈよりも短かった場合を不良として示した。ドロップアウト特性は、信頼性評価時にドロップアウトカウンターを用いて３μｓ相当の記録抜けの個数をカウントすることにより行った。ドロップアウト特性の判断基準は、記録抜けの個数が１分間に５０個以下の場合に良とした。
【００６３】
表２に示したように、実施例１〜実施例５によれば、信頼性についてもドロップアウト特性についても共に良好な結果を得られた。これに対して比較例１および比較例２では、ドロップアウト特性を改善することができなかった。これは、比較例１では第１の研磨テープにおける研磨剤の大きさが小さいので磁性層の表面にある極端に大きな突起を十分に除去することができなかったためと考えられる。また、比較例２では、第１の研磨テープにおける研磨剤のモース硬度が磁性層に含まれる研磨剤のモース硬度よりも大きいので、磁性層の表面にキズをつけてしまったためと考えられる。
【００６４】
更に、比較例３および比較例４では信頼性を改善することができなかった。これは、比較例３では、第２の研磨テープにおける研磨剤の大きさが大きく、かつ凹条部もないので、ブレードに似た表面有機物捕獲効果の働きがなかったためと考えられる。また、比較例４では、第２の研磨テープにおける研磨剤のモース硬度が磁性層に含まれる研磨剤のモース硬度よりも小さいので、研磨テープの磨耗が急速に進み、表面処理効果が得られなくなったためと考えられる。その結果、比較例３および比較例４では、ＥＳＣＡによるＣｌ／ＦｅまたはＣ／Ｆｅの減少が見られなくなり、結果的に表層有機物リッチとなり、ヘッドクロッグが生じてしまったものと考えられる。
【００６５】
加えて、比較例５ではドロップアウト特性を改善することができなかった。これは、第１の研磨テープにおける研磨剤の大きさが大きいので、磁性層に対して、研磨テープが粗すぎて突起あるいは強磁性粉末を除去する効果もないばかりか、傷も発生してしまったためと考えられる。
【００６６】
なお、第１の研磨テープを用いた表面処理のみを行った場合、および第２の研磨テープを用いた表面処理のみを行った場合は、磁気記録媒体の走行が不可能となり特性の評価を行えなかった。
【００６７】
すなわち、第１の研磨テープを用いた表面処理と、第２の研磨テープを用いた表面処理とを行い、第１の研磨テープにおける研磨剤の大きさを２０００メッシュ以上４０００メッシュ以下、モース硬度を磁性層に含まれる研磨剤のモース硬度以下とし、第２の研磨テープにおける研磨剤の大きさを８０００メッシュ以上、モース硬度を磁性層に含まれる研磨剤のモース硬度以上とし、凹条部を設けるようにすれば、信頼性およびドロップアウト特性を改善できることが分かった。
【００６８】
以上、実施の形態および実施例を挙げて本発明を説明したが、本発明は上記実施の形態および実施例に限定されるものではなく、種々変形が可能である。例えば、上記実施の形態および実施例では、磁気記録媒体の構成を具体的に挙げて説明したが、上記実施の形態において説明した全ての層を備える必要はなく、また、他の層を更に備えていてもよい。また、上記実施の形態では磁性層１３が単層構造である場合について説明したが、磁性層１３は積層構造としてもよく、この場合、積層数は何層でもよい。
【００６９】
また、上記実施の形態および実施例で説明した成膜方法や成膜条件は、他の成膜方法や成膜条件に変更することも可能である。
【００７０】
【発明の効果】
以上説明したように本発明の磁気記録媒体の製造方法によれば、モース硬度が磁性層に含まれる研磨剤のモース硬度以下であり、かつ大きさが２０００メッシュ以上４０００メッシュ以下の研磨剤を含む第１の研磨テープを用いて磁性層を表面処理する第１の工程と、この第１の工程を行ったのち、モース硬度が磁性層に含まれる研磨剤のモース硬度以上であり、かつ大きさが８０００メッシュ以上の研磨剤を含む第２の研磨テープを用いて磁性層を表面処理する第２の工程とを含むようにしたので、磁性層の表面に存在する固定不十分な強磁性粉末、および乾燥過程で磁性層の表面に染み出した樹脂ないし有機物などの結合剤成分を、第１の研磨テープおよび第２の研磨テープの組合せにより効果的に除去することができる。よって、磁気記録媒体の走行中に強磁性粉末が磁性層から脱離して磁気ヘッドに付着するいわゆるパウダーと呼ばれる汚れ、あるいは結合剤成分が磁気ヘッドに付着するいわゆるウィスカーと呼ばれる汚れが確実に防止され、ドロップアウトあるいはヘッドの目詰まりを防ぎ、優れた信頼性を実現することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る磁気記録媒体の製造方法を工程順に表す断面図である。
【図２】本発明の一実施の形態に係る磁気記録媒体の製造方法に用いられる表面処理装置の構成を表す斜視図である。
【図３】図２に示した表面処理装置の動作を説明するための斜視図である。
【符号の説明】
１０…積層テープ、１１…非磁性支持体、１２…下地層、１２Ａ…下地塗布層、１３…磁性層、１３Ａ…磁性塗布層、１４…バックコート層、１００…表面処理装置、１１０…バックアップローラ、１２０…研磨テープ、１３０…研摩テープ保持部、１３１…基台、１３２…巻出し側リール、１３３…巻取り側リール、１３４…ガイドローラ、１３５…スライド板、θ…抱き角[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a magnetic recording medium having a magnetic layer, and more particularly to a method for manufacturing a magnetic recording medium including a step of surface-treating a magnetic layer with an abrasive tape.
[0002]
[Prior art]
A magnetic recording medium such as a magnetic recording tape or a magnetic disk is used in a magnetic recording / reproducing apparatus as a peripheral device such as an audio apparatus, a video apparatus or a computer apparatus. There are two types of magnetic recording media: coating type and thin film type. Among these, coating type ones use ferromagnetic powders such as iron or iron oxide, binders and various additives as organic solvents. A magnetic recording layer is formed by coating, drying, smoothing and curing a dispersed and kneaded magnetic coating on a non-magnetic support.
[0003]
In these various magnetic recording media, higher image quality, longer time, or digital recording have been developed in recent years, and there is a demand for excellent electromagnetic conversion characteristics as well as higher density recording.
[0004]
In order to realize excellent electromagnetic conversion characteristics, it is very important to make the magnetic layer thin and uniform, as well as smooth the tape surface. As one of the methods, a method has been proposed in which a lower layer made of a non-magnetic paint is provided on a non-magnetic support, and an upper layer made of a magnetic paint is applied while the lower layer is undried to provide a magnetic layer ( For example, see Patent Document 1.)
[0005]
However, depending on the method of smoothing the tape surface or reducing the thickness of the magnetic layer, there is a problem that the magnetic head is soiled and the electromagnetic conversion characteristics deteriorate.
[0006]
Magnetic head contamination causes clogging (head clog) of the video head. For example, it is unreliable when used in a mode in which virgin tape is recorded and played back (only two passes) and changed one after another (for example, during dubbing), and dirt at this time is mainly a binder component. is there. The main component of the binder component is that the component in the binder of the magnetic recording medium floats near the surface of the magnetic layer and adheres to the magnetic head due to the sliding contact between the magnetic recording medium and the magnetic head.
[0007]
In terms of running durability, in the case of a one-reel type linear running tape, the head mount becomes dirty due to long-time shuttle running, and the content of the dirt is mainly a ferromagnetic powder called so-called powder. Dirt and binder components called so-called whiskers are roughly divided into main dirt. The main contamination of the ferromagnetic powder is that particulate components such as insufficiently fixed ferromagnetic powder existing on the surface of the magnetic layer of the magnetic recording medium are detached while the magnetic recording medium is running and adhere to the magnetic head. Further, such a granular component that is insufficiently fixed on the surface of the magnetic layer has a problem that it increases the surface roughness of the magnetic layer and causes wear on the surface of the magnetic head.
[0008]
In order to obtain good reliability and running durability, a nitrocellulose resin having a degree of polymerization of 30 to 50 is added to the binder of the magnetic paint at a ratio of 2 to 8 parts by weight with respect to 100 parts by weight of the magnetic powder. Although a method has been proposed (see, for example, Patent Document 2), the addition of a nitrocellulose resin has a problem that it causes a thickening of the magnetic paint and makes it difficult to reduce the thickness of the magnetic layer.
[0009]
Similarly, in order to obtain good reliability and running durability, a method of adding an abrasive and a lubricant to the magnetic layer to remove dirt on the magnetic head during running has been proposed. When it is raised, the wear of the head becomes severe. On the other hand, when the abrasiveness is lowered, the function of cleaning the deposits that cause head dirt and clogging is lowered. Therefore, the addition of an abrasive has a limit in keeping head wear low and preventing head clogging and contamination.
[0010]
Therefore, in order to solve these problems, a surface treatment for cleaning or polishing the surface of the magnetic recording medium with a nonwoven fabric or an abrasive tape is performed. For example, Patent Document 3 discloses a technique in which a magnetic layer of a magnetic recording medium is subjected to a surface smoothing process using a calendar, and then the surface of the magnetic layer is polished using a polishing tape. Surface treatment using such an abrasive tape can easily obtain a high effect in a short time compared to blade treatment.
[0011]
Further, Patent Document 4 proposes that the effect of the surface treatment is further enhanced by bringing the polishing tape and the magnetic recording medium into sliding contact with each other with their sliding directions being non-parallel.
[0012]
[Patent Document 1]
Japanese Patent Publication No. 6-93297
[Patent Document 2]
JP-A-5-334654
[Patent Document 3]
JP 63-259830 A
[Patent Document 4]
JP 2000-90433 A
[0013]
[Problems to be solved by the invention]
However, most of the surface treatment techniques disclosed so far are mainly effective for stains caused by ferromagnetic powders, and are insufficient for stains caused by binder components.
[0014]
The present invention has been made in view of such problems, and an object of the present invention is to effectively remove not only the ferromagnetic powder but also the binder component and suppress the occurrence of clogging of the magnetic head and the occurrence of clogging. It is to provide a method for manufacturing a recording medium.
[0015]
[Means for Solving the Problems]
A method of manufacturing a magnetic recording medium according to the present invention is to manufacture a magnetic recording medium having a magnetic layer containing a ferromagnetic powder, a binder, and an abrasive, and the Mohs hardness of the abrasive contained in the magnetic layer. After performing the first step of surface-treating the magnetic layer using a first polishing tape containing a polishing agent having a hardness of not more than hardness and a size of not less than 2000 mesh and not more than 4000 mesh, And a second step of surface-treating the magnetic layer using a second polishing tape having a Mohs hardness equal to or greater than the Mohs hardness of the abrasive contained in the magnetic layer and having a size of 8000 mesh or more. It is a waste.
[0016]
In the method for manufacturing a magnetic recording medium according to the present invention, in the first step, the Mohs hardness is equal to or less than the Mohs hardness of the abrasive contained in the magnetic layer, and the size includes an abrasive having a size of 2000 mesh to 4000 mesh. The magnetic layer is surface-treated using the polishing tape 1 to remove the insufficiently fixed ferromagnetic powder existing on the surface of the magnetic layer. After the first step is performed, in the second step, the second polishing includes a polishing agent having a Mohs hardness equal to or greater than the Mohs hardness of the polishing agent contained in the magnetic layer and having a size of 8,000 mesh or more. The magnetic layer is surface-treated using a tape, and the binder component floating on the surface of the magnetic layer is removed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
FIG. 1 shows a method for manufacturing a magnetic recording tape which is a magnetic recording medium according to an embodiment of the present invention. First, as shown in FIG. 1A, for example, a nonmagnetic support 11 as a base film is prepared. The nonmagnetic support 11 is not particularly limited, and for example, a polyester film made of polyethylene terephthalate or polyethylene-2,6-naphthalate, or an aramid film can be used. The thickness of the nonmagnetic support 11 is desirably about 3.0 μm to 15.0 μm, for example.
[0019]
Next, nonmagnetic inorganic particles are blended and dispersed, for example, in an amount of about 250% to 1300% by weight with respect to the binder, and the resulting dispersion is dispersed in an organic solvent to prepare an undercoat paint. By applying this undercoat paint to the nonmagnetic support 11, an undercoat layer 12A is formed as shown in FIG.
[0020]
Non-magnetic inorganic particles are not particularly limited, but for example, carbon black, aluminum oxide, chromium oxide, silicon carbide, titanium oxide, silicon oxide, calcium carbonate, α-iron oxide, kaolin, graphite, mica, titanium carbide or calcium phosphate Can be used. The shape of the non-magnetic inorganic particles may be spherical, needle-like, plate-like or the like. In consideration of the smoothness of the undercoat layer 12A, the size of the nonmagnetic inorganic particles is, for example, a needle having a major axis length of, for example, 0.2 μm or less, and if spherical, a particle size of, for example, 0.2 μm or less. If so, the diameter of the plate is preferably set to 0.2 μm or less, for example.
[0021]
As the binder, any resin material used in ordinary coating-type magnetic recording media can be used, and the type is not particularly limited. Examples of typical binders include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer. Polymer, vinyl chloride-acrylonitrile copolymer, acrylate ester-vinylidene chloride copolymer, methacrylate ester-vinylidene chloride copolymer, methacrylate ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride -Acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, polyvinyl acetal, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, phenol Shi resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, or urea - formaldehyde resins.
[0022]
Above all, at least some of them are -SO _Three M group (M represents an alkali metal such as Na or K or an alkyl group), -SO _Four At least one of M group (M represents an alkali metal or alkyl group such as Na or K), carboxylate group, amino acid group, aminosulfonic acid group, phosphone group, phosphine group, amino group, etc. is introduced. What is done is desirable.
[0023]
As the organic solvent, for example, ethers, esters, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, or organic chlorine compound solvents can be used depending on the type of binder.
[0024]
Various kneaders can be used for kneading and dispersing the constituent materials of the undercoat paint. Examples of the kneader include an extruder, a sand mill, a dyno mill, a pressure kneader, a continuous kneader, a dissolver, a two roll mill, a three roll mill, a ball mill, a pebble mill, a side grinder, a high speed impeller disperser, a high speed stone mill, and a high speed. An impact mill, a disperser, a high-speed mixer, a homogenizer, or an ultrasonic disperser may be mentioned.
[0025]
There is no restriction | limiting in particular as a coating method of a base layer coating material, A well-known system is employable. For example, die coating method, gravure coating method, knife coating method, wire bar coating method, doctor blade coating method, reverse roll coating method, dip coating method, air knife coating method, calendar coating method, squeeze coating method, kiss coating method Further, an extrusion coater of a fantin coating method or an extrusion method can be used.
[0026]
Subsequently, about 100 parts by weight of the ferromagnetic powder is blended with, for example, about 10 to 30 parts by weight of a binder, and further, about 5 to 20 parts by weight of an abrasive is further dispersed and dispersed. The liquid is dispersed in an organic solvent to prepare a magnetic layer paint. As shown in FIG. 1A, the magnetic coating layer 13A is provided by applying the magnetic coating material onto the base coating layer 12A while the base coating layer 12A is not yet dried.
[0027]
As the ferromagnetic powder, any conventionally known one can be used, and may be an oxide magnetic powder or a metal magnetic powder. Examples of the oxide magnetic powder include γ-diiron trioxide (γ-Fe ₂ O _Three ), Γ-Fe added with cobalt (Co) ₂ O _Three , Triiron tetroxide (Fe _Three O _Four ), Fe added with cobalt _Three O _Four Γ-Fe coated with cobalt ₂ O _Three , Fe coated with Co _Three O _Four Or chromium oxide (CrO ₂ ) Is used. Examples of the metal magnetic powder include iron, cobalt, nickel, iron-cobalt alloy, iron-nickel alloy, iron-cobalt-nickel alloy, cobalt-nickel alloy, iron-cobalt-boron alloy, iron-cobalt-chromium-boron alloy. , Manganese-bismuth alloy, manganese-aluminum alloy, or iron-cobalt-vanadium alloy are used, and metal components such as aluminum, silicon, titanium, chromium, manganese, copper, and zinc are used for the purpose of improving these various characteristics. Or a rare earth element containing yttrium may be added. Further, for example, Fe _Five C ₂ It is also possible to use iron carbide or iron nitride. As the binder, the same one as the base coating layer 12A can be used. As the abrasive, for example, an inorganic powder such as an aluminum oxide powder having a Mohs hardness of about 8 to 9 is preferably used.
[0028]
Note that a dispersant such as lecithin, an antistatic agent such as carbon black, or a rust inhibitor may be added to the base coating layer 12A and the magnetic coating layer 13A as necessary. As these dispersant, antistatic agent, and rust preventive agent, any conventionally known materials can be used and are not limited at all. Furthermore, a known lubricant may be added, and for example, fatty acids and fatty acid esters are used.
[0029]
Moreover, you may mix | blend an inorganic pigment with the base coating layer 12A and the magnetic coating layer 13A. As the inorganic pigment, for example, aluminum oxide, chromium oxide, silicon oxide, titanium oxide, silicon carbide, calcium carbonate, α-iron oxide, kaolin, graphite, mica, or titanium carbide can be used.
[0030]
Further, a curable resin can be added to the base coating layer 12A and the magnetic coating layer 13A in order to improve durability. Specifically, thermosetting resins such as polyisocyanate compounds and polyepoxy compounds, or electron beam reactive curable resins can be used. These may be used alone or in combination of two or more.
[0031]
After the magnetic coating layer 13A is formed, the magnetic coating layer 13A in an undried state is subjected to magnetic field orientation treatment, and further subjected to surface rendering by calendering using a super calender roll or the like. . The temperature at that time is usually preferably 50 ° C. to 250 ° C., the linear pressure is preferably 50 kg / cm to 400 kg / cm, for example, and the coating speed is preferably 20 m / min to 600 m / min, for example.
[0032]
After performing the surface smoothing process, the base layer 12 and the magnetic layer 13 are formed by performing a curing process, as shown in FIG. In addition, you may perform a burnish process or a blade process as needed. The thickness of the magnetic layer 13 is preferably 0.1 μm to 4.0 μm, for example, and more preferably 0.01 μm to 2.5 μm.
[0033]
Subsequently, as shown in FIG. 1 (C), a carbon black paint is applied to the back surface of the non-magnetic support 11 to form a back coat layer 14 and slitting to 3/4 inch width to form a laminated tape. 10 is assumed. The back coat layer 14 is provided for the purpose of improving the runnability of the magnetic recording medium, preventing charging and preventing transfer, and is formed by adding a binder and various known additives for the back coat layer. As the binder for the backcoat layer 14, the same binder as that for the underlayer 12 and the magnetic layer 13 can be used.
[0034]
After slitting, the magnetic layer 13 is subjected to a surface treatment with a polishing tape. FIG. 2 shows a surface treatment apparatus used for this surface treatment. In the surface treatment apparatus 100, a backup roller 110 that holds the laminated tape 10 and a polishing tape holding unit 130 that holds the polishing tape 120 are disposed to face each other. The backup roller 110 has a smooth peripheral surface for running the laminated tape 10. The polishing tape 120 has, for example, a polishing layer containing an abrasive and a binder. The polishing tape holding unit 130 has a configuration in which a base 131 is provided with an unwinding reel 132, a winding reel 133, and a pair of guide rollers 134. The base 131 is attached to a slide plate 135 and can be moved in the direction of arrow A by a cylinder (not shown) provided on the slide plate 135. The polishing tape 120 is wound between the unwinding reel 132 and the winding reel 133, and is pulled out to the backup roller 110 side by a pair of guide rollers 134.
[0035]
In this surface treatment apparatus 100, as shown in FIG. 3, the polishing tape holding unit 130 is moved in the direction of arrow A, that is, toward the backup roller 110, and the polishing tape 120 between the pair of guide rollers 134 is wound around the backup roller 110. A predetermined holding angle θ with respect to the laminated tape 10 is set. Then, by rotating the backup roller 110 in the direction indicated by the arrow B, the laminated tape 10 is caused to travel in the direction indicated by the arrow C, and the unwinding side reel 132, the winding side reel 133, and the pair of guide rollers 134 are rotated. Thus, the polishing tape 120 is caused to travel in the direction of arrow D. Thereby, the surface treatment of the magnetic layer 13 is performed by bringing the laminated tape 10 into sliding contact with the polishing tape 120.
[0036]
Here, in this embodiment, the cause of head clogging (head clogging), which is the most fatal problem in dropout and running durability, is insufficiently fixed on the surface of the magnetic layer 13. Focusing on the fact that it is broadly divided into ferromagnetic powder and binder components such as organic substances deposited and unevenly distributed on the surface of the magnetic layer 13, surface treatment is performed several times using two types of polishing tapes 120. ing.
[0037]
First, the first step of surface-treating the magnetic layer 13 using a first polishing tape having a Mohs hardness equal to or less than the Mohs hardness of the abrasive contained in the magnetic layer 13 and a size of 2000 mesh to 4000 mesh. After performing this first step, the magnetic layer 13 is formed using a second polishing tape having a Mohs hardness equal to or greater than the Mohs hardness of the abrasive contained in the magnetic layer 13 and a size of 8000 mesh or greater. The 2nd process of surface-treating is performed. The first abrasive tape is suitable for removing the ferromagnetic powder, and the second abrasive tape is suitable for removing the binder component. Thus, by selecting and combining the first polishing tape and the second polishing tape according to the object to be removed, more effective surface treatment is possible, and dropout characteristics and running durability are improved.
[0038]
Furthermore, for the second polishing tape, for example, it is preferable to use a tape having a concave portion that is not parallel to the tape edge on the surface. This is because such a concave portion comes into contact with the magnetic layer 13 like a blade, and the binder component can be effectively removed. Further, as disclosed in the above-mentioned Patent Document 4, it is not necessary to make the sliding contact direction between the polishing tape and the magnetic recording medium non-parallel to each other, and the sliding contact direction between the polishing tape and the magnetic recording medium can be changed. This is because, even when parallel, the concave stripe portion does not become parallel to the magnetic recording medium, so that a good surface treatment can be performed. Furthermore, since the concave portion can collect wear powder generated during polishing, it can achieve a high-quality polishing finish without causing so-called whitening. In addition, the concave stripe portion that is not parallel to the tape edge is a straight line provided to intersect with the tape edge at an angle larger than 0 ° and smaller than 180 °, or a curved shape. The one provided in
[0039]
Among them, as the second polishing tape, for example, it is preferable to use a tape having a concave portion that forms a hexagonal image line. This is because a higher effect can be obtained. In addition, this groove part is formed by the Benard cell phenomenon generate | occur | produced in a resin coating film, for example, when apply | coating the resin coating film which consists of a coating agent containing an inorganic component, and forming a grinding | polishing layer. Spot-like recesses may be formed at the corners of the hexagonal image line, and these spot-like recesses also collect the abrasion powder generated during polishing in the same manner as the recesses. be able to.
[0040]
The number of surface treatments in the first step and the second step may be one time or a plurality of times. When performing a plurality of times, it is preferable to perform the second step after performing a plurality of times in the first step. However, the first step and the second step are repeated in order. It may be. Further, in this surface treatment step, surface treatment with another polishing tape is performed as necessary before the first step, between the first step and the second step, or after the second step. Also good. Thereby, the magnetic recording medium is completed.
[0041]
As described above, in this embodiment, the Mohs hardness is equal to or less than the Mohs hardness of the abrasive contained in the magnetic layer, and the first abrasive tape containing the abrasive having a size of 2000 mesh or more and 4000 mesh or less is used for the magnetic property. A first step of surface-treating the layer, and after performing the first step, a Mohs hardness equal to or greater than the Mohs hardness of the abrasive contained in the magnetic layer and a size of 8000 mesh or more is included. And a second step of surface-treating the magnetic layer using the second polishing tape, so that the insufficiently fixed ferromagnetic powder present on the surface of the magnetic layer 13 and the magnetic layer 13 in the drying process A binder component such as a resin or an organic substance that oozes out to the surface can be effectively removed. Therefore, it is ensured that the so-called “powder” that the ferromagnetic powder is detached from the magnetic layer 13 and adheres to the magnetic head while the magnetic recording medium 10 is running, or the so-called “whisker” that the binder component adheres to the magnetic head. Therefore, it is possible to prevent dropout or clogging of the head and realize excellent reliability.
[0042]
【Example】
Furthermore, specific examples of the present invention will be described.
[0043]
(Example 1)
A magnetic recording medium 10 was produced in the same manner as in the above embodiment. First, an undercoat layer coating was prepared, and the undercoat layer 12A was formed by applying the undercoat layer to the nonmagnetic support 11 made of a polyethylene terephthalate film having a thickness of 8.0 μm. At that time, the underlayer paint is prepared by kneading with a kneader using the following materials, further diluted with a solvent, dispersed in a sand mill, and polyisocyanate (Nippon polyurethane curing agent “Coronate L (trade name)” immediately before coating. ) Was added.
[0044]
Nonmagnetic inorganic particles:
α-iron oxide (major axis length 0.15 μm) 100 parts by weight
Binder:
3.5 parts by weight of polyester-polyurethane (number average molecular weight = 10,000, polar group: containing sulfonate sodium salt 0.08 mmol / g, polyester main component: isophthalic acid, adipic acid-neopentyl glycol, ethylene glycol, urethanized isocyanate: Diphenylmethane diisocyanate)
6.5 parts by weight of vinyl chloride copolymer (average polymerization degree = 305, polar group: containing potassium sulfate 0.08 mmol / g, other main substituents: epoxy 0.8 mmol / g containing, hydroxyl group 0.3 mmol / G content)
lubricant:
1 part by weight of isooctyl palmitate
1 part by weight of stearic acid
solvent:
80 parts by weight of methyl ethyl ketone
80 parts by weight of toluene
40 parts by weight of cyclohexanone
[0045]
Subsequently, a magnetic layer coating material was prepared, and the undercoat layer 12A was applied while undried to form a magnetic coating layer 13A. At that time, the magnetic layer coating material is kneaded with a kneader using the following materials, further diluted with a solvent, then dispersed in a sand mill, and immediately before application, a polyisocyanate (Japanese polyurethane curing agent “Coronate L (trade name)” ) And added through a homogenizer.
[0046]
Fine ferromagnetic powder:
100 parts by weight of iron-cobalt alloy (major axis length 0.15 μm)
Binder:
10 parts by weight of polyester-polyurethane (number average molecular weight = 21000, polar group: 0.12 mmol / g of sulfonic acid sodium salt, polyester main component: isophthalic acid-ethylene glycol, urethanized isocyanate: diphenylmethane diisocyanate)
10 parts by weight of vinyl chloride copolymer (average degree of polymerization = 200, polar group: containing potassium sulfate 0.08 mmol / g, other main substituents: containing epoxy 0.8 mmol / g, hydroxyl 0.3 mmol / g Contains)
Inorganic powder (abrasive):
10 parts by weight of aluminum oxide powder (alpha conversion = 85%, average particle size = 0.23 μm, Mohs hardness 9)
lubricant:
1 part by weight of butyl stearate
Stearylamide 0.5 parts by weight
solvent:
20 parts by weight of methyl ethyl ketone
20 parts by weight of toluene
10 parts by weight of cyclohexanone
[0047]
Next, a magnetic field orientation process was performed, the film was appropriately dried and wound up, a calendar process was performed, and a curing process was performed to form the underlayer 12 and the magnetic layer 13. After that, a carbon black paint was applied to the back surface of the nonmagnetic support 11 to form a backcoat layer 14 and slitting to a 3/4 inch width.
[0048]
After slitting, surface treatment was performed as described in the above embodiment using the first polishing tape and the second polishing tape shown in Table 1. The processing conditions were a line speed of 300 m / min, a polishing tape holding angle of 120 °, a tension of 200 g, and a polishing tape feed speed of 20 mm / min. As a first polishing tape, Nippon Micro Coating polishing tape GC2000 (abrasive SiO 2 ₂ : Surface treatment using abrasive size 2000 mesh: Mohs hardness 6) is performed once, and as a second polishing tape, a polishing tape WA10000 made by Nihon Micro Coating (Abrasive A1203: abrasive size 10,000 mesh: Mohs hardness 9: Surface treatment was performed twice using a concave portion formed by the Benard cell phenomenon. As a result, a magnetic recording medium of Example 1 was obtained.
[0049]
[Table 1]

[0050]
(Example 2)
As shown in Table 1, as a first abrasive tape, Nippon Micro Coating abrasive tape GC3000 (abrasive SiO 2 ₂ : Surface treatment using abrasive size 3000 mesh: Mohs hardness 6) was performed twice, and as a second abrasive tape, Nippon Microcoating abrasive tape D10000 (abrasive diamond: abrasive size 10,000 mesh: Mohs hardness 10: A magnetic recording medium was fabricated in the same manner as in Example 1 except that the surface treatment using the concave portion formed by the Benard cell phenomenon was performed once.
[0051]
(Example 3)
As shown in Table 1, as a first polishing tape, Nippon Micro Coating polishing tape GC4000 (abrasive SiO 2 ₂ : Surface treatment using abrasive size 4000 mesh: Mohs hardness 6) is performed three times. As a second abrasive tape, abrasive tape WA8000 made by Nihon Micro Coating (Abrasive Al) ₂ O _Three A magnetic recording medium was prepared in the same manner as in Example 1 except that the surface treatment was performed twice using: Abrasive size 8000 mesh: Mohs hardness 9: Recessed portion formed by Benard cell phenomenon) .
[0052]
Example 4
As shown in Table 1, as a first polishing tape, a polishing tape WA2000 manufactured by Japan Micro Coating (Abrasive Al) ₂ O _Three : Surface treatment using abrasive size 2000 mesh: Mohs hardness 9) is performed once, and as a second abrasive tape, a polishing tape D8000 made by Nippon Micro Coating (abrasive diamond: abrasive size 8000 mesh: Mohs hardness 10: A magnetic recording medium was fabricated in the same manner as in Example 1 except that the surface treatment using the concave portion formed by the Benard cell phenomenon was performed once.
[0053]
(Example 5)
As shown in Table 1, as a first polishing tape, a polishing tape WA3000 made by Nippon Micro Coating (Abrasive Al) ₂ O _Three A magnetic recording medium was prepared in the same manner as in Example 1 except that: abrasive size 3000 mesh: Mohs hardness 9) was used.
[0054]
(Comparative Example 1)
As Comparative Example 1, as shown in Table 1, the first abrasive tape was coated with Nippon Micro Coating abrasive tape GC6000 (abrasive SiO 2 ₂ A magnetic recording medium was prepared in the same manner as in Example 1 except that: abrasive size 6000 mesh: Mohs hardness 6) was used. That is, the size of the abrasive in the first polishing tape was made smaller than in Example 1.
[0055]
(Comparative Example 2)
As Comparative Example 2, as shown in Table 1, it was carried out except that a Japanese microcoating abrasive tape D3000 (abrasive diamond: abrasive size 3000 mesh: Mohs hardness 10) was used as the first abrasive tape. A magnetic recording medium was produced in the same manner as in Example 2. That is, the Mohs hardness of the abrasive in the first polishing tape was larger than that in Example 2, and was larger than the Mohs hardness 9 of the abrasive contained in the magnetic layer 13.
[0056]
(Comparative Example 3)
As Comparative Example 3, as shown in Table 1, the second polishing tape was coated with Japan Micro Coating Abrasive Tape WA6000 (Abrasive Al ₂ O _Three A magnetic recording medium was prepared in the same manner as in Example 3, except that: abrasive size 6000 mesh: Mohs hardness 9: no recess was used. That is, the size of the polishing agent in the first polishing tape was made larger than that in Example 3, and the concave portion was eliminated.
[0057]
(Comparative Example 4)
As Comparative Example 4, as shown in Table 1, the second polishing tape was coated with Nippon Micro Coating Abrasive Tape K8000 (Abrasive Cr ₂ O _Three A magnetic recording medium was prepared in the same manner as in Example 4 except that: Abrasive size 8000 mesh: Mohs hardness 8: Recessed portion formed by Benard cell phenomenon) was used. That is, the Mohs hardness of the abrasive in the second polishing tape was smaller than that in Example 4, and was smaller than the Mohs hardness 9 of the abrasive contained in the magnetic layer 13.
[0058]
(Comparative Example 5)
As Comparative Example 5, as shown in Table 1, the first abrasive tape was coated with Japan Micro Coating Abrasive Tape WA1000 (Abrasive Al ₂ O _Three A magnetic recording medium was prepared in the same manner as in Example 5 except that: abrasive size 1000 mesh: Mohs hardness 9) was used. That is, the size of the abrasive in the first polishing tape was made larger than that in Example 5.
[0059]
(Evaluation)
For the obtained magnetic recording media of Examples 1 to 5 and Comparative Examples 1 to 5, the amount of the binder component on the surface of the magnetic layer was measured. The results are shown in Table 2. The amount of the binder component on the surface of the magnetic layer was measured by Cl-2p spectrum by X-ray photoelectron spectroscopy (ESCA), which is an analysis method capable of obtaining information up to 10 nm from the surface of the magnetic recording medium. And an integrated intensity ratio between the C-1S spectrum and the Fe-2p (3/2) spectrum.
[0060]
[Table 2]

[0061]
Examples of specific conditions for ESCA measurement include X-ray intensity: 8 kV-200 W, X-ray anode type: monochromator Al, measurement X-ray: AlKα ray, and measurement time: within 10 minutes. As a specific apparatus used for such measurement, ESCA3200 type manufactured by ULVAC-PHI can be used.
[0062]
In addition, the slit magnetic recording medium was incorporated into a cassette, and reliability and dropout characteristics were measured. The results are also shown in Table 2. Here, the “reliability” was measured by the time until the head clog was generated by switching the virgin tape one recording pass and one reproduction pass. In Table 2, the case where the time until the head clog was generated was 40 h or more was shown as good, and the case where it was shorter than 40 h was shown as bad. The dropout characteristic was performed by counting the number of missing recordings corresponding to 3 μs using a dropout counter during reliability evaluation. The criterion for determining the dropout characteristics was good when the number of missing records was 50 or less per minute.
[0063]
As shown in Table 2, according to Examples 1 to 5, good results were obtained with respect to both reliability and dropout characteristics. On the other hand, in Comparative Example 1 and Comparative Example 2, the dropout characteristics could not be improved. This is presumably because, in Comparative Example 1, the size of the abrasive in the first polishing tape was small, so that extremely large protrusions on the surface of the magnetic layer could not be sufficiently removed. In Comparative Example 2, it is considered that the surface of the magnetic layer was scratched because the Mohs hardness of the abrasive in the first polishing tape was larger than the Mohs hardness of the abrasive contained in the magnetic layer.
[0064]
Further, in Comparative Example 3 and Comparative Example 4, the reliability could not be improved. This is presumably because in Comparative Example 3, the size of the abrasive in the second polishing tape was large and there was no concave portion, so that the surface organic matter capturing effect similar to that of the blade did not work. In Comparative Example 4, since the Mohs hardness of the abrasive in the second polishing tape is smaller than the Mohs hardness of the abrasive contained in the magnetic layer, the abrasion of the polishing tape proceeds rapidly and the surface treatment effect cannot be obtained. It is thought that it was because of. As a result, in Comparative Example 3 and Comparative Example 4, the decrease in Cl / Fe or C / Fe due to ESCA was not observed, and as a result, the surface organic matter was rich, and it was considered that head clogging occurred.
[0065]
In addition, in Comparative Example 5, the dropout characteristic could not be improved. This is because the size of the polishing agent in the first polishing tape is large, so that the polishing tape is too rough for the magnetic layer to not only remove protrusions or ferromagnetic powder, but also scratches have occurred. it is conceivable that.
[0066]
When only the surface treatment using the first polishing tape is performed and when only the surface treatment using the second polishing tape is performed, the magnetic recording medium cannot be run and the characteristics can be evaluated. There wasn't.
[0067]
That is, the surface treatment using the first polishing tape and the surface treatment using the second polishing tape are performed, the size of the abrasive in the first polishing tape is 2000 mesh or more and 4000 mesh or less, and the Mohs hardness is set. The Mohs hardness of the abrasive contained in the magnetic layer is set to be equal to or less than the Mohs hardness of the abrasive in the second polishing tape, and the Mohs hardness is set to be equal to or greater than the Mohs hardness of the abrasive contained in the magnetic layer. By doing so, it was found that reliability and dropout characteristics could be improved.
[0068]
The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the configuration of the magnetic recording medium has been specifically described, but it is not necessary to include all the layers described in the above-described embodiments, and further include other layers. It may be. Moreover, although the case where the magnetic layer 13 has a single-layer structure has been described in the above embodiment, the magnetic layer 13 may have a stacked structure, and in this case, the number of stacked layers may be any number.
[0069]
Further, the film formation method and film formation conditions described in the above embodiment modes and examples can be changed to other film formation methods and film formation conditions.
[0070]
【The invention's effect】
As described above, according to the method for manufacturing a magnetic recording medium of the present invention, the Mohs hardness is equal to or less than the Mohs hardness of the abrasive contained in the magnetic layer, and the abrasive contains 2000 to 4000 mesh. A first step of surface-treating the magnetic layer using the first polishing tape, and after performing the first step, the Mohs hardness is equal to or greater than the Mohs hardness of the abrasive contained in the magnetic layer Includes a second step of surface-treating the magnetic layer using a second polishing tape containing an abrasive of 8000 mesh or more, and an insufficiently fixed ferromagnetic powder present on the surface of the magnetic layer, In addition, the binder component such as resin or organic matter that oozes out on the surface of the magnetic layer during the drying process can be effectively removed by the combination of the first polishing tape and the second polishing tape. Therefore, dirt called so-called powder, in which the ferromagnetic powder is detached from the magnetic layer and adheres to the magnetic head while the magnetic recording medium is running, or so-called whisker, which is so-called whisker where the binder component adheres to the magnetic head, is reliably prevented. , Dropout or clogging of the head can be prevented, and excellent reliability can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a method of manufacturing a magnetic recording medium according to an embodiment of the invention in the order of steps.
FIG. 2 is a perspective view showing a configuration of a surface treatment apparatus used in a method for manufacturing a magnetic recording medium according to an embodiment of the present invention.
3 is a perspective view for explaining the operation of the surface treatment apparatus shown in FIG. 2; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Laminated tape, 11 ... Nonmagnetic support, 12 ... Undercoat layer, 12A ... Undercoat layer, 13 ... Magnetic layer, 13A ... Magnetic coat layer, 14 ... Backcoat layer, 100 ... Surface treatment apparatus, 110 ... Backup roller 120 ... Abrasive tape, 130 ... Abrasive tape holder, 131 ... Base, 132 ... Unwinding reel, 133 ... Rewinding reel, 134 ... Guide roller, 135 ... Slide plate, .theta.

Claims (4)

A method for producing a magnetic recording medium having a magnetic layer comprising a ferromagnetic powder, a binder, and an abrasive,
A first surface treatment is performed on the magnetic layer using a first polishing tape having a Mohs hardness equal to or less than the Mohs hardness of the abrasive contained in the magnetic layer and containing an abrasive having a size of 2000 mesh or more and 4000 mesh or less. And the process of
After performing this first step, the magnetic properties are obtained using a second polishing tape having a Mohs hardness equal to or higher than the Mohs hardness of the abrasive contained in the magnetic layer and containing an abrasive having a size of 8000 mesh or more. And a second step of surface-treating the layer. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the second polishing tape has a groove on the surface that is not parallel to the tape edge. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the second abrasive tape has a concave portion that forms a hexagonal image line on the surface. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the second abrasive tape has a concave portion formed on the surface by the Benard cell phenomenon.

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