JP4549031B2 - Magnetic disk substrate holding member and method of manufacturing the same - Google Patents

Description

【００２３】
【表２】

【００２４】
【表３】

【００２５】
【発明の効果】
以上のように、本発明によれば、主成分となるフォルステライトと導電成分となる酸化鉄とを平均粒径が０．９μｍ以下となるように粉砕し焼成してなる、２ＭｇＯ・ＳｉＯ_２を主結晶相とし、副結晶相としてＭｇＦｅ_２Ｏ_４、Ｆｅ_３Ｏ_４、Ｆｅ_２Ｏ_３の少なくとも１種の結晶のみを有する焼結体からなる磁気ディスク基板用保持部材であって、前記セラミック焼結体は、モース硬度が７を超える非常に硬い化合物の含有量が０．５重量％以下であるとともに、Ａｌ_２Ｏ_３の含有量がＺｒＯ_２の含有量よりも少なく０．１重量％以下とすることによって、磁気ディスク基板との熱膨張差が小さく、高精度加工が可能であり、静電気除去効果を持ち合わせるとともに、磁気ディスク装置のクラッシュ要因となる高硬度の異物の含有量が少ないので、信頼性の高い保持部材を提供することができる。しかも、上記セラミック焼結体の製造工程において、ジルコニアビーズを用いたビーズミルで原料の粉砕、混合を行なうことで、磁気ディスク装置のクラッシュの要因となる高硬度の異物の混入量が少なく、粒度分布が非常にシャープな原料を比較的安価に製造できるので、見掛け比重が大きくてボイド占有率の低い、緻密化された信頼性の高い保持部材を提供することができる。
【図面の簡単な説明】
【図１】本発明の磁気ディスク基板用保持部材の製造工程で使用するビーズミルの模式図である。
【図２】一般的な原料粉末の粉砕に使用されるボールミルの模式図である。
【符号の説明】
１：粉砕ビーズ
２：スラリー供給口
３：回転ローター
４：スクリーン
５：スラリー出口
１１：粉砕ボール
１２：原料スラリー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk substrate holding member such as a spacer used for holding a magnetic disk substrate, and a method of manufacturing the same.
[0002]
[Prior art]
Conventionally, a magnetic disk device used as an external recording devices for computers and consumer electronics is the fixed to the rotating shaft hub, the embedded a magnetic disk substrate and the spacer alternately by tightening, the magnetic disk substrate regular intervals It was supposed to be fixed and held. Then, with rotating the rotary shaft, and a magnetic disk substrate, by moving in a non-contact state of the magnetic head to the magnetic disk substrate, and writing of information to the magnetic disk substrate, it is read Riogyo information It was.
[0003]
Incidentally, in recent years, there has been a demand for higher density magnetic disk substrates and larger capacity of magnetic disk devices . To that end, the surface of the magnetic disk substrate is highly smoothed and flattened, and the deformation of the magnetic disk substrate is reduced. It is necessary to prevent distortion and make the distance between the magnetic head and the magnetic disk substrate as small as possible . For this reason , the magnetic disk substrate is formed of ceramics, glass, or the like, and a magnetic disk substrate holding member (hereinafter simply referred to as a holding member) such as a spacer for holding each magnetic disk substrate is subjected to a thermal expansion difference from the magnetic disk substrate. It is proposed to form a ceramic sintered body containing forsterite as a main component, which can be processed with high accuracy, with little deformation and little deterioration due to temperature change and deterioration over time.
[0004]
Further, the magnetic disk substrate may static electricity is generated, the ceramic sintered body of this static electricity since the information recorded on the magnetic disk substrate is Re hyperemesis be destroyed, mainly of the forsterite It has been shown that iron oxide is added to make it semiconductive to release charges charged on the magnetic disk substrate and prevent destruction of recorded information (see Patent Document 1).
[0005]
[Patent Document 1]
JP 2002-193659 A [Patent Document 2]
Japanese Patent Laid-Open No. 2002-230933 [Patent Document 3]
JP-A-2002-216449 [0006]
[Problems to be solved by the invention]
When a holding member made of a ceramic sintered body is used by being incorporated in a magnetic disk device in which the distance between the magnetic head and the magnetic disk substrate is 0.1 μm or less, foreign matter is caught between the magnetic head and the magnetic disk substrate, There has been a problem that foreign matters are pressed against the magnetic disk substrate by the magnetic head, destroying the magnetic head and the recording layer on the magnetic disk substrate, making it impossible to write or read information.
[0007]
That is, the ceramic sintered body forming the holding member is a polycrystalline body obtained by baking and solidifying a ceramic raw material, and there are a large number of voids on the surface, and the ceramic is subjected to grinding to obtain a predetermined shape. Grinding flaws are formed on the surface of the sintered body, but foreign matter such as grinding powder, polishing powder, or degranulated powder generated during production of the holding member has entered the voids or grinding flaws on the surface of the holding member. These foreign matters are spilled from voids or grinding flaws due to vibration during driving of the magnetic disk device, etc., and the foreign matter that has fallen on the magnetic disk substrate is pressed by the magnetic head or bites into the magnetic head. It was.
[0008]
In the manufacturing process of the ceramic sintered body, the ball mill shown in FIG. At this time, when the raw material slurry 12 is pulverized with the pulverization balls 11 made of alumina, foreign matters are mixed, and when these foreign matters are very hard and have a Mohs hardness of 7, the above problem is remarkably generated.
[0009]
Therefore, in order to remove foreign matter such as grinding powder , polishing powder, or degranulated powder entering the voids of the holding member and grinding scratches formed so as to have a predetermined size and shape by grinding or polishing, ultraviolet rays or ozone cleaning by washing using a detergent, bubble washing is different cleaning process of ultrasonic cleaning or the like is we row, it also completely remove the foreign matter as using any method of washing difficult.
[0010]
In addition, there are proposals to reduce the above-mentioned foreign matter by heat-treating the holding member or applying a resin film, but there are also problems such as cost increase and film peeling, and there remains anxiety in terms of reliability. (See Patent Document 2 and Patent Document 3).
[0011]
[Means for Solving the Problems]
As a result of various studies to solve the above problems, the magnetic disk substrate holding member has an average particle size of 0.9 μm or less of forsterite as a main component and iron oxide as a conductive component. Ceramic sintered body having 2MgO · SiO ₂ as a main crystal phase and having only at least one crystal of MgFe ₂ O ₄ , Fe ₃ O ₄ , and Fe ₂ O ₃ as a sub-crystal phase. This ceramic sintered body has a Mohs hardness of more than 7 in a compound content of 0.5% by weight or less and is extremely hard among the compounds, which may contribute to the crash of the magnetic disk device. A highly reliable holding member can be provided by suppressing the content of Al ₂ O _{3 that} is very high to be less than 0.1% by weight less than the content of ZrO ₂ .
[0012]
As the configuration and production method made you holding member with reduced amount of mixed Al ₂ O ₃ which is a compound having a Mohs hardness of more than 7 to 0.1 wt% or less, in the step of pulverizing the holding member material, It was found that grinding with a bead mill using zirconia beads is also effective from the viewpoint of quality and capital investment.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0014]
The holding member for a magnetic disk substrate of the present invention is for holding the magnetic disk substrate at regular intervals. Then, the magnetic disk substrate holding member of the present invention comprises 2MgO · SiO formed by pulverizing and firing forsterite as a main component and iron oxide as a conductive component so that the average particle size becomes 0.9 μm or less. ₂ is composed of a ceramic sintered body having only a main crystal phase and at least one crystal of MgFe ₂ O ₄ , Fe ₃ O ₄ , Fe ₂ O ₃ as a sub-crystal phase. The ceramic sintered body has a Mohs hardness. The content of a very hard compound having a ratio of more than 7 is 0.5% by weight or less, and the content of Al ₂ O ₃ is less than the content of ZrO ₂ and is 0.1% by weight or less.
[0015]
For example, when the compound of the above Mohs hardness of 7, as as Al ₂ O ₃ or SiC is present, even in a foreign matter grinding powder and abrasive powder or shedding dust that has entered into the grinding flaws and voids of the holding member, will be those Mohs hardness of 7 or more compounds are present, due to vibration, etc. such foreign objects at startup magnetic disk device, dropped from voids or grinding scratches, the possibility that the cause of the crash of the magnetic disk device Very expensive. In particular Al ₂ O ₃ the process of manufacturing retaining member material, generally used may be a grinding balls for raw material powder grinding, more wear, the grinding balls during pulverization, it is present in the holding member many, moreover, because very hard and Mohs hardness 9, a problem of the aforementioned magnetic disk drive crash that occur markedly. Therefore, it is particularly important that the content of Al ₂ O ₃ is 0.1 wt% or less. As in the present invention, reducing as much as possible the Mohs hardness of 7 or more compounds, the possibility of the magnetic disk device crash is that the low Kunar, leads to supply high holding member of reliability.
[0016]
Hereinafter, a method for manufacturing the magnetic disk substrate holding member of the present invention will be described.
First, a powder obtained by adding iron oxide as a conductive component to forsterite as a main component as a starting material and water are mixed to form a slurry, and the slurry is pulverized by a bead mill shown in FIG. As the pulverized beads used in the bead mill, zirconia beads are used. The aforementioned slurry is supplied from the slurry supply port 2, stirred by the rotary rotor 3, pulverized by grinding with the zirconia pulverized beads 1, and discharged from the slurry outlet 5 through the screen 4. This slurry is pulverized and pulverized. When the average particle size reaches 0.9 μm or less , all the slurry is discharged, and then a binder is added and spray-dried to produce granulated powder. After forming this granulated powder into a predetermined shape at a pressure of about 1 ton / cm ² , it is fired at a temperature of 1200 to 1500 ° C., and subjected to grinding and polishing, thereby producing a magnetic disk substrate holding member having a predetermined shape. To do.
[0017]
The magnetic disk substrate holding member manufactured by the above manufacturing process is obtained by pulverizing and firing forsterite as a main component and iron oxide as a conductive component so that the average particle size is 0.9 μm or less. This ceramic sintered body is composed of a ceramic sintered body having 2MgO.SiO ₂ as a main crystal phase and only at least one kind of crystals of MgFe ₂ O ₄ , Fe ₃ O ₄ , and Fe ₂ O ₃ as a sub-crystal phase. The content of a very hard compound having a Mohs hardness exceeding 7 is 0.5% by weight or less, and the content of Al ₂ O ₃ is less than the content of ZrO ₂ and is suppressed to 0.1% by weight or less. Can be a holding member.
[0018]
That is, Mohs hardness of 7 or less forsterite as the main component (2MgO · SiO _2), using an iron oxide, thus the grinding in a bead mill using zirconia milling beads, the content of the compound exceeding the Mohs hardness 7 it is possible to 0.5 wt% or less, the content of _Al 2 _{O 3} can be 0.1 wt% or less.
[0019]
【Example】
A raw material obtained by mixing a powder obtained by adding iron oxide as a conductive component to forsterite as a main component and water with a stirrer into a slurry is used as a bead mill (invention example) shown in FIG. 1 and a ball mill shown in FIG. The actual particle size distribution was measured by crushing with an average particle size of 0.9 μm or less by the two types of crushing methods of (Comparative Example). The grinding conditions are as shown in Table 1. Next, to prepare a granulated powder was added to the spray dried Vine da to the slurry after the pulverization. This granulated powder was molded into a predetermined shape at a pressure of 1 ton / cm ² and fired at a temperature of 1280 ° C. to obtain a sintered body. About the obtained sintered compact, composition quantitative analysis by ICP, apparent specific gravity, and void occupation rate were measured, and the results are shown in Table 2. Table 3 shows the Mohs hardness of the constituent compounds for reference.
[0020]
First, in Table 1, in order to satisfy the target particle size, in the ball mill which is a comparative example, the pulverization time is significantly long as 160 hours, but the one using the bead mill which is the embodiment of the present invention is very short. Grinding in time was possible. Further, comparing the particle size distributions of the two, it can be seen that the bead mill has a much sharper distribution than the ball mill. Although the ball mill liner and the pulverized ball 11 shown in FIG. 2 may be made of zirconia, shortening of the pulverization time cannot be expected, and zirconia is very expensive and the capital investment is expected to be enormous. Therefore, it is hard to say that it is an effective method.
[0021]
Next, in Table 2, in the comparative example using a ball mill is Al ₂ O ₃ in the wear from the liner and grinding balls are mixed from about 2 wt%, in the present invention embodiment using a bead mill Al ₂ O ₃ Is very low at 0.06% by weight in terms of impurities in the starting material. On the contrary, in the bead mill, ZrO ₂ contamination was confirmed to be about 0.15% by weight, but the amount of contamination was small, and ZrO ₂ is a material with a Mohs hardness of 7, so the influence on the crash of the magnetic disk device is small. From the apparent specific gravity and void occupancy measurement results, it was confirmed that the bead mill pulverization was more dense and the voids were smaller than the ball mill pulverization. This is because the particle size distribution is very sharp by bead mill grinding, and an effect of reducing foreign matters that adversely affect the crash of the magnetic disk device can be expected.
[0022]
[Table 1]

[0023]
[Table 2]

[0024]
[Table 3]

[0025]
【The invention's effect】
As described above, according to the present invention, 2MgO · SiO ₂ obtained by crushing and firing forsterite as a main component and iron oxide as a conductive component so as to have an average particle size of 0.9 μm or less is obtained. A holding member for a magnetic disk substrate comprising a sintered body having only a crystal of MgFe ₂ O ₄ , Fe ₃ O ₄ , and Fe ₂ O ₃ as a main crystal phase and a sub-crystal phase. In the bonded body, the content of a very hard compound having a Mohs hardness of more than 7 is 0.5% by weight or less, and the content of Al ₂ O ₃ is less than the content of ZrO ₂ and is 0.1% by weight or less. By doing so, the difference in thermal expansion from the magnetic disk substrate is small, high-precision processing is possible, it has a static elimination effect, and the content of high-hardness foreign matter that causes a crash of the magnetic disk device Because small, it is possible to provide a highly reliable holding member. Moreover, in the manufacturing process of the ceramic sintered body, the raw material is pulverized and mixed in a bead mill using zirconia beads, so that the amount of high-hardness foreign matter that causes a crash of the magnetic disk device is small, and the particle size distribution However, since a very sharp raw material can be manufactured at a relatively low cost, it is possible to provide a dense and highly reliable holding member having a large apparent specific gravity and a low void occupancy.
[Brief description of the drawings]
FIG. 1 is a schematic view of a bead mill used in a manufacturing process of a magnetic disk substrate holding member of the present invention.
FIG. 2 is a schematic view of a ball mill used for pulverizing general raw material powders.
[Explanation of symbols]
1: grinding beads 2: slurry supply port 3: rotating rotor 4: screen 5: slurry outlet 11: grinding ball 12: raw material slurry

Claims (2)

2MgO · SiO _{2 formed} by pulverizing and firing forsterite as a main component and iron oxide as a conductive component to have an average particle size of 0.9 μm or less is used as a main crystal phase, and MgFe ₂ as a sub crystal phase. A holding member for a magnetic disk substrate made of a ceramic sintered body having only at least one crystal of O ₄ , Fe ₃ O ₄ , and Fe ₂ O ₃ , wherein the content of the compound having a Mohs hardness of more than 7 is 0.00. A magnetic disk substrate holding member, wherein the holding member is 5% by weight or less and the content of Al ₂ O ₃ is less than the content of ZrO ₂ and is 0.1% by weight or less.   A method for manufacturing a magnetic disk substrate holding member according to claim 1, wherein zirconia beads are produced by mixing forsterite as a main component, iron oxide as a conductive component, and water into a slurry by mixing with a stirrer. A process of pulverizing the bead mill to have an average particle size of 0.9 μm or less, a process of adding a binder to the pulverized slurry and spray-drying to obtain a granulated powder, and pressing the granulated powder And a step of firing the magnetic disk substrate holding member.

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