JPS6398832A - Manufacture of rotary blade body and magnetic recording medium - Google Patents

Abstract

PURPOSE:To decrease the number of granular components removed from the surface of magnetic substance layer by using a rotary blade body comprising a rotary body whose cross section is circular and a blade provided at the outer circumference of the rotary body so as to apply grinding to the magnetic layer. CONSTITUTION:The rotary blade body consists of the rotary body 1 and the blade 3 provided at the outer circumference 2 of the rotary body along its rotary shaft. A cylinder whose cross section is circular is used for the rotary body 1. Furthermore, the blade 3 is preferably made of one of sapphire, alumina and thermet and the number of blades is >=one being 2-32 preferably. Then the magnetic layer coated onto the support is subject to surface smoothing processing, the said rotary blade is subject to grinding to remove the granular components or adhesives exfoliated easily. Thus, the removed substance from the surface of the magnetic layer is reduced and dropout or clogging is decreased.

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to a method for producing a magnetic recording medium having a basic structure consisting of a non-magnetic support and a magnetic layer provided on the support, and a method for use in this method. The present invention relates to a rotating blade body.

[Background of the Invention] Magnetic recording media in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support are generally used as magnetic recording media for audio, video, or computers. ing.

Such a magnetic recording medium uses a magnetic paint in which a binder component such as a resin component and a particulate component such as ferromagnetic powder are dispersed in a solvent, and a non-magnetic support 1. ni coating 1 (j L.

The applied IHj layer is subjected to treatments such as magnetic field orientation treatment, drying treatment, and surface +-smoothing treatment. In general, the surface of a magnetic layer manufactured in this way is extremely smooth, with the granular components firmly fixed to the magnetic layer. However, according to the investigation of IJI individuals who have not yet developed IJI, there are particulate components such as ferromagnetic powder that are insufficiently fixed on the surface of the magnetic layer. Ta.

Such insufficiently fixed particulate components may detach during running and land on the magnetic head, causing clogging of the magnetic head 11, and may also cause dropouts in, for example, video tapes. Sometimes. Since the j and Y of the ferromagnetic powder near the surface of the magnetic layer decrease due to such detachment of the ferromagnetic powder, there is also the problem that electromagnetic conversion characteristics deteriorate (reduction in output) due to repeated running.

The present inventor has invented a method of grinding the surface of a magnetic layer as a method of reducing the occurrence of such dropouts, clogging, and output reduction, and this invention has already been filed (Japanese Patent Application No. 13184/1983). issue).

That is, the present invention removes granular components or magnetic particles that are easily detached by grinding the surface of the magnetic layer, which has been smoothed on the surface, using a high-hardness grinding tool such as a diamond wheel or a fixed sapphire blade. This removes deposits on the surface of the magnetic layer and reduces the amount of substances detached from the surface of the magnetic layer. By grinding the magnetic layer in this manner, it is possible to effectively prevent dropouts and clogging, as well as a decrease in output due to long running times.

Against this background, the present inventor further investigated the grinding of the magnetic layer surface, and as a result, invented a grinding tool suitable for grinding the magnetic layer of a magnetic recording medium, and by using this, the running durability was further improved. It has been found that a good magnetic recording medium can be manufactured.

[Object of the invention] An object of the present invention is to provide a method for manufacturing a magnetic recording medium having good running durability.

Furthermore, the present invention provides a novel grinding tool suitable for manufacturing such magnetic recording media with good running durability [1]
target

[Summary of Part II] The present invention resides in a rotary blade body comprising a rotary body having a circular cross section and at least one blade provided on the outer circumference of the rotary body along its rotation axis.

Furthermore, the present invention provides a method of applying the above-mentioned rotating blade to the surface of the magnetic layer after smoothing the surface of the magnetic layer coated on a non-magnetic support and comprising ferromagnetic powder dispersed in a binder. Provided is a method for manufacturing a magnetic recording medium, characterized in that a grinding process is performed by bringing the medium into contact with the magnetic recording medium under rotation.

[Effect of IJI] By using the specific grinding tool of the present invention, the magnetic +1 layer can be ground by ωF to a good f.

Therefore, the number of granular particles such as ferromagnetic powder that easily comes off from the surface of the magnetic layer is reduced, so that the magnetic helad 11 is clogged and dropouts are caused by the tax deduction of these granular components during running. It is possible to manufacture a magnetic recording medium with less .

Furthermore, since the number of ferromagnetic powders that are subtracted from the surface of the magnetic layer is reduced, there is little decrease in the amount of strong (a ti) powder even when running repeatedly. Magnetic recording media with low raw power output can be manufactured.

In addition, when a hardening agent is used as a component for forming the magnetic layer, most of the unreacted hardening agent on the surface of the magnetic layer is removed, so dust and the like will not adhere to the magnetic layer after the magnetic recording medium is manufactured. Therefore, it is possible to manufacture a magnetic recording medium in which draw and blowout caused by such deposits are less likely to occur. Furthermore, since the magnetic head is less likely to be contaminated with unreacted hardened material, it is possible to manufacture a magnetic recording medium in which the occurrence of clogging of the magnetic head due to dust adhesion to the magnetic head is less likely.

``9.1 Detailed description of town'' Magnetic recording media are usually produced by coating a non-magnetic support 4 with magnetic paint, performing magnetic field orientation treatment, hardening treatment, surface) L digestion treatment, etc. Manufactured by cutting into desired shape.

A magnetic recording medium consists of a nonmagnetic support and a magnetic layer provided on the support. The magnetic layer consists of a particulate component such as ferromagnetic powder and a binder in which the particulate component is dispersed. The binder is composed of the 84 fat component and a curing agent that may be added as desired.

Coating of the magnetic layer can be carried out according to a conventional method. For example, a magnetic paint is prepared by cross-dispersing magnetic layer forming components such as a resin component, a ferromagnetic powder, and an abrasive and a hardening agent blended as desired with a solvent, and this magnetic paint is applied onto a non-magnetic support. method can be used.

The resin component is selected from resins commonly used as resin components of magnetic paints. Examples of resin components include vinyl chloride copolymers (e.g., vinyl chloride/drunken vinyl copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinyl acetate/acrylic intoxicant copolymer,
! Vinyl l111! Chemical Hini IJ Ten copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/acid-resistant vinyl copolymer, vinyl chloride copolymer into which polar groups such as -5O, Na or -5o2Na and epoxy groups have been introduced), Cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, polyurethane resin (e.g., polyester polyurethane resin, polarity such as -3O, Na or -5o2Na), (introduced) polyurethane resins, polycarbonate polyurethane resins).

Furthermore, when a curing agent is used, a polyisocyanate compound is usually used. The polyisocyanate compound is selected from those commonly used as curing agent components for polyurethane resins and the like. Examples of polyisocyanate compounds include a reaction product of tolylene diisocyanate and 1 mol of trimethylolpropane (eg, Desmodur L-75 (manufactured by Bayer)), 3 mol of a diisocyanate such as xylylene diisocyanate or hexamethylene diisocyanate. and 1 mole of trimethylolpropane, biuret addition compound of 3 moles of hexamethylene diisocyanate, incyanurate compound of 5 moles of tolylene diisocyanate, incyanurate compound of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate. Mention may be made of nurate addition compounds, polymers of inphorone diisocyanate and diphenylmethane diisocyanate.

Further, when performing curing treatment by electron beam irradiation, a compound having a reactive double bond (eg, vinyl chloride copolymer acrylate, urethane acrylate) can be used.

In the present invention, it is preferable to use a combination of a hard resin such as a vinyl chloride copolymer and a flexible resin such as a polyurethane resin as the resin component.

When using a combination of a highly hard resin such as a vinyl chloride copolymer and a flexible resin such as a polyurethane resin, the blending weight rUY ratio of the former to the latter is usually 9:1 to 1. Within the range of 5:5 (preferably 9:1 to 6:4)
). And when using a hardening agent, usually
■-The blending weight ratio of the resin component and curing agent is 9:1 to 5.
:5 (preferably 9:1 to 6:4).

Generally, when using ferromagnetic powder with low hardness such as ferromagnetic metal fine powder.

γ-Fe 20. Use a larger amount of binder than when using a harder material such as. In this case, the amount of resin, such as polyurethane resin, which affects flexibility, is usually increased.

Since the binder tends to soften as the amount of polyurethane resin used increases, a method is usually used to maintain the hardness of the binder by increasing the amount of a hardening agent such as a polyisocyanate compound.

When using a polyurethane resin as a resin component and a polyinsyanate compound as a curing agent, the blending weight ratio of the polyurethane resin and the polyisocyanate compound is usually 1:0.8 to 1:2 (preferably 1:1
~1:1.5). By doing so, even when using ferromagnetic metal fine powder with low hardness, softening of the binder due to the use of polyurethane resin can be effectively prevented.

The total weight of the resin component and curing agent is 1, and the ferromagnetic powder is 10.
Usually 10 to 100 parts by weight (15 to 4 parts by weight)
0 double positive part).

An example of the ferromagnetic powder used in Unreleased 1!1 is γ-Fe.
20. ferromagnetic powders based on metal oxides, such as ferromagnetic powders based on dissimilar metals and metal oxides, such as γ-Fe 20° containing other components such as cobalt, and ferromagnetic powders based on dissimilar metals and metal oxides, such as iron, cobalt, or nickel. Examples include fine ferromagnetic metal powders containing magnetic metals.

In particular, the present invention is advantageous when used as a method for producing a magnetic recording medium using fine ferromagnetic metal powder. In other words, even if a large amount of hardening agent is used in conjunction with the use of ferromagnetic metal fine powder, the amount of deposits on the 1gi layer or magnetic head can be reduced, reducing dropouts and magnetic heads. A magnetic recording medium with less clogging can be manufactured.

When using a ferromagnetic metal fine powder, it is a ferromagnetic metal fine powder containing iron, cobalt or nickel, and has a specific surface area of 42rn'/g or more (particularly preferably 45rn'/g).
rr'/g or more) is preferably a ferromagnetic metal fine powder.

As an example of this ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and the metal content is 8% by weight.
0% by weight or more of at least one ferromagnetic metal or alloy (e.g., Fe, CO1Ni, Fe-Co, Fe-Ni
, Go-Ni, Co-N1-Fe), and other components (e.g., An, Si,
S, Sc, Ti, V, Cr, Mn, Cu, Zn, Y, M
o, Rh, Pd, Ag, Sn, Sb, B, Ba, Ta,
W, Re, Au, Hg, Pb, P, La, Ce, Pr,
Mention may be made of alloys that may contain Nd, Te, Bi). Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide.

Methods for producing these ferromagnetic powders are already known, and the ferromagnetic powder used in the present invention can also be produced according to known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. In particular, it is preferable to use acicular ferromagnetic powder.

The above resin component, curing agent, and ferromagnetic powder are mixed and dispersed together with a solvent (e.g., methyl ethyl ketone, dioxane, cyclohexanone, ethyl acetate) that is normally used in the preparation of magnetic paint to obtain a magnetic paint. Crosstalk dispersion can be performed according to conventional methods.

In addition to the bipedal component, the magnetic paint contains abrasives (e.g.
α-A M 203, Cr203), antistatic agents (e.g., carbon black), lubricants (e.g., fatty acids, fatty acid esters, silicone oil), dispersants, and other commonly used additives or fillers. ) may of course be included. When a saturated fatty acid having a carbon number of 10 to 22 is used as a 41 lubricant in 4'r, the saturated fatty acid tends to be oriented in a layered manner on the surface of the magnetic layer by grinding using a rotating blade body described below. Since the fatty NI film oriented in this manner has high strength and also has good lubricity, it has the advantage that the running properties of the magnetic recording medium are improved to -1.

The magnetic paint thus prepared is applied to the non-magnetic support I-. The coating method can be carried out using a conventional coating method such as a method using a reverse roll.

The coating layer of the magnetic coating material is applied so that the thickness of the magnetic layer of the obtained magnetic recording medium is usually within the range of 0.5 to logm.

A commonly used non-magnetic support can be used, and the non-magnetic support generally has a thickness S of 3 to 5.
0 gm (preferably 5 to 30 gm) is used.

A back layer (backing layer) may be provided on the surface of the non-magnetic support used in the present invention that is not coated with magnetic paint.Normally, the back layer is the surface of the non-magnetic support that is not coated with magnetic paint. A pack layer type I in which particulate components such as abrasives and antistatic agents and a binder are dispersed in an organic solvent on the surface.
This is a layer provided by applying & coating $1.

Note that an adhesive layer may be attached to the surface of the nonmagnetic support on which the magnetic paint and the back layer forming paint are applied.

Usually, the applied layer of magnetic paint is subjected to a treatment for orienting the ferromagnetic powder contained in the applied layer of magnetic paint, that is, a magnetic field orientation treatment, and then dried and smoked.

After drying in this way, the coating layer is treated with a surface-leveling treatment (
For example, a super calender roll is used for the 0 surface smoothing treatment in which 1Y is applied. By performing the 0 surface smoothing treatment, the pores generated by the removal of the solvent by dry blasting are eliminated, and the ferromagnetism in the magnetic layer is Since the filling rate of the powder is symmetrical, a magnetic recording medium with high electromagnetic conversion characteristics can be obtained.

In the method for producing undeveloped IJI, the surface of the magnetic layer that has been subjected to surface smoothing treatment is ground using a rotating blade.

However, if a curing agent is used as a forming component of the binder, at this stage, only one of the curing agents contained in the magnetic layer is used.
Usually, more than 90% by weight of the curing agent is contained in the magnetic layer in an unreacted state, so a curing treatment is performed to react at least 50% by weight of the curing agent (particularly preferably 80-L or more). It is preferable to grind it later.

The curing process includes a heat curing process and an electron beam irradiation curing process, and either method can be used in the present invention.

Through this curing treatment, the unreacted curing agent contained in the surface-smoothed magnetic layer forms a three-dimensional network crosslinked structure with resin components such as vinyl chloride copolymer and polyurethane resin. react to.

The steps of heat treatment are already well known, and the heat treatment can also be performed in the present invention according to these methods.

For example, in heat treatment, the heating waiting time is usually 40°C or more - L (
(preferably within the range of 50 to 80°C), heating time is usually 2
It is set to 0 hours or more (preferably between 24 hours and 71 hours). Further, the process of curing treatment by electron beam irradiation is already known, and the heat treatment can be performed according to these methods in the present invention as well.

The thus cured laminate is then cut into a desired shape.

The cutting can be carried out under normal conditions using a normal cutting machine such as a slitter.

The surface of the magnetic layer of the thus hardened and cut laminate is ground using a rotating blade.

FIG. 1 is a perspective view showing an example of a rotating blade body.

As shown in FIG. 1, the rotating blade body includes a rotating body 1,
The rotary body l, which is composed of at least one blade 3 provided on the outer circumference 2 of the rotary body along the rotation axis of the rotary body l, has a circular cross section perpendicular to the rotation axis, and is usually cylindrical. A shape of the shape is used. The diameter of the circular cross section of the rotating body l is usually in the range of 10 to 50 m.

Further, the length can be appropriately set according to the width of the magnetic recording medium to be ground. For example, when grinding is performed after slitting, the length of the rotating body 1 is usually set to 1.1 to 10 times the width of the magnetic recording medium to be ground.

Note that the material forming the rotating body 1 is usually a metal such as iron, brass, or stainless steel.

It is necessary that at least one blade 2 is provided on the outer circumferential portion 2 of the rotating body described in -1-, but the number is preferably in the range of 2 to 32, and further 2 to 32.
The blades, which are particularly preferably within the range of 10 blades, are provided on the outer circumference 2 of the rotating body in a direction along the rotational axis of the rotating body, and usually the blades are arranged parallel to the rotational axis of the rotating body. It is installed on the outer periphery.

Figure 2 shows an example of the blades provided on the outer periphery of the above-mentioned rotating body.

As shown in FIG. 2, the blade 3 is generally a triangular prism with a triangular cross section perpendicular to its length.

The size of the blade can be set as appropriate depending on the size of the rotating body, the number of blades provided on the outer periphery of the rotating body, etc., but usually the blade bottom a in FIG.
The blade length b is in the range of 0.5 to 10 mm, and the blade height b is in the range of 3 to 10 mm. The length C of the blade is set corresponding to the length of the above-mentioned normal rotating body.

Since the blade grinds the magnetic layer of the magnetic recording medium, it is made of a material that has a hardness equal to or higher than the components contained in the magnetic layer. They are typically made of materials such as sapphire, alumina, zirconium oxide, zirconia, silicon nitride, silicon carbide, diamond, and cemented carbide. In particular, it is preferable to use sapphire.

The blade 3 is attached to the outer peripheral portion 2 of the rotating body along the rotational axis direction of the rotating body l using, for example, a screw.

FIG. 3 shows a side view of the rotary blade body of the present invention.

As shown in FIG. 3, the arrangement angle 0 of the blade 3, that is, the angle θ formed by the virtual line connecting the apex of the blade 3 and the center of rotation of the rotary blade body and the base of the blade, is
Preferably, the angle is within the range of 30 to 150 degrees. Further, the apex of the blade usually protrudes by 1 mm or more (preferably 2 mm or more) W from the surface of the rotating body.

Grinding of a magnetic layer using such a rotary blade usually involves running the magnetic layer to be ground while keeping the surface and surface of the magnetic layer at a constant distance.
This is done by bringing it into contact with the rotating blade body. That is, when grinding the surface of the magnetic layer, a tension of usually 30 to 100 g and 78 mm is applied in the length direction of the laminate consisting of the nonmagnetic support and the magnetic layer, and the tension is usually 60 to 1200 m. Contact is made while running at a speed within the range of /min.

The rotational speed of the rotating blade body in contact with the magnetic layer is usually i
It is set within the range of oo to 6000 revolutions/minute (preferably 150 to 500 revolutions). Further, the contact angle (wrap angle) between the magnetic layer and the rotating blade body is usually 30 to 18
It is set within the range of 0 degrees (preferably 30 to 120 degrees).

Further, it is preferable that the rotating direction of the rotary blade body is opposite to the traveling direction of the magnetic layer. Grinding efficiency is improved by bringing the rotary blade into contact with the rotating blade body in the opposite direction.

The above treatment removes particulate components such as ferromagnetic powder or abrasive material protruding from the surface of the magnetic layer, as well as unreacted curing agent and surface deposits (e.g. magnetic Dust in the air that adheres to the surface when manufacturing the recording medium is scraped off together with the binder near the surface of the magnetic layer (generally at a height of 0.01 to 5 gm).
The surface of the magnetic layer is smoothed.

Furthermore, it is preferable to perform a wiping treatment on the surface of the magnetic layer thus ground, that is, by removing grinding debris generated by grinding, it is possible to further reduce the occurrence of dropouts.

An example of a wiping material is a suede-like nonwoven fabric with a single layer structure in which bundles of polyester fibers of o, oi to 0.09 denier are bound and tightly intertwined without containing a binding component such as polyurethane (e.g., Ecsaine (trade name) manufactured by Toshi ■) and nonwoven fabrics made by bonding polyester fibers with a binding component such as polyurethane (for example, Vilene (trade name) manufactured by Nippon Vilene ■), which are especially suitable for the present invention. In this case, it is preferable to use the former suede-like nonwoven fabric.

In addition, although the method described above has mainly been described in which the magnetic layer and the rotary blade are brought into contact after cutting the entire laminate that has been subjected to a smoothing treatment on the surface, the present invention is not limited to this order. For example, a method of contacting the material while cutting or a method of contacting the material before cutting can be used.

Furthermore, since the curing reaction proceeds gradually without any hardening treatment, the surface of the magnetic layer can be ground after one surface smoothing treatment without any particular hardening treatment.

In the following margins, Examples and Comparative Examples of the present invention will be shown. In the Examples and Comparative Examples, the expression "part" means "r hair amount part".

[Example 1] A magnetic paint was prepared by cross-dispersing the magnetic paint composition described in F in a ball mill until it became uniform.

After adjusting the viscosity of the obtained magnetic coating material, it was coated onto the surface of a polyethylene terephthalate support with a thickness of 10 gm using a reverse roll so that the thickness of the magnetic layer was 3.0 mm.

Magnetic paint composition Ferromagnetic metal fine powder Ioo part (composition: Fe96%, Ni4%, specific surface area: 45rn'/g) Vinyl chloride/vinyl acetate Φ Maleic anhydride copolymer 14 parts (400Xl
l0A Nippon Zeon Co., Ltd.) polyurethane resin
12 parts Tuboran N-2304, Polyurethane 1 part) Polyisocyanate compound 12 parts (Desmodur Shi-75, manufactured by Bayer AG) α-Alumina 10 parts Stearic acid 5 parts Butyl stearate 5811 Carbon black 1 part Methyl ethyl ketone 325 Back layer type L1 below for each part
12. A back layer forming paint was prepared by cross-dispersing the paint composition in a ball mill until it became uniform.

After adjusting the viscosity of the obtained back layer forming coating material, it was coated on the back surface of the support coated with the above magnetic coating material using a reverse roll so that the thickness of the back layer was 0.7 gm.

Back layer forming coating composition Carbon black 35 parts (V average particle size: 0.05 pm) α-Alumina 1.8 parts (V average particle size: 0.15 JLm Maximum particle size: 0.3 pm) Nitrocellulose 20 parts Polyurethane resin Tsuboran N in the io part
-2304, [manufactured by this polyurethane]) Polyisocyanate compound 10 parts (Cholenate L, manufactured by Nippon Polyurethane Hayashi)) Methyl ethyl ketone 600 parts The non-magnetic support coated with the magnetic paint and the back layer paint was coated with A laminate consisting of a non-magnetic support, a magnetic layer and a back layer was prepared by subjecting the product to a magnetic field orientation treatment using a 3000 Gauss magnet in a dry state, and after roughly drying it to a super calender treatment.

This laminate was heat-treated at 60°C for 24 hours to harden the polyisocyanate compound contained in the magnetic layer, and then slit to 8 mm, and the surface of the magnetic layer was slit using a rotating blade under the conditions described below. Grinding is carried out, and further,
A wiping operation was performed on the ground magnetic layer surface using suede-like nonwoven 1 (i (product name: Ecsaine, manufactured by Toshi)), in which polyester fibers of 0.1 to 0.9 denier are intertwined with each other facing east. An 8 mm video tape was manufactured by applying the same method.

Grinding using a rotating blade body A cylindrical metal (length: 35 mm, diameter: 20 mm, cavity diameter: 12 mm) has an equilateral triangular prism shape with a length of 35 mm and a side of 5 mm in cross section. A rotating blade body including one sapphire blade (blade installation angle: 0:65 degrees) was prepared.

This rotary blade body was rotated at 1000 revolutions/minute in the opposite direction to the traveling direction of the magnetic layer, and a tension of 50 g/min was applied to the laminate.
The surface of the magnetic layer was ground by bringing the magnetic layer of the laminate into contact with a rotating blade at a contact angle of 120 degrees under a tension of 8 mm at 4-t-'l-.

The obtained 8 mm video tape was run using a Shuppan video recorder (FUJ 1X-8), and 15g5, -
The number of 18 dB dropouts occurring per minute was measured.

In addition, using the above-mentioned apparatus, the number of instantaneous [J jams] that occurred was measured by running a length of tape that ran for 90 minutes at a normal running speed.

Furthermore, using the above device, the obtained tape was repeatedly run 10 times, and the playback output at the 10th time was measured when the playback output at the first time was set as OdB (output decrease).
.

In addition, in the examples and comparative examples shown below, draw 2
The number of dropouts, instantaneous clogging, and output reduction were measured using the methods described above.

Table 1 shows the measurement results for the number of dropouts, the number of instantaneous clogging, and the low output F.

[Comparative Example 1] An 8 mm video tape was produced in the same manner as in Example 1 except that the magnetic layer was not ground using a rotating blade.

Table 1 shows the measurement results of the number of dropouts, the number of instantaneous clogging, and the decrease in output.

[Comparative Example 2] An 8 mm video tape was produced in the same manner as in Example 1, except that instead of grinding the magnetic layer with the rotating blade body, the magnetic layer was ground using the informal blade described below. did.

Sapphire blade treatment Sapphire blade with a 60 degree angle at the tip (width: 5mm)
, length 35 mm, manufactured by Kyocera ■) and the magnetic layer were brought into contact with each other at a contact angle of 80 degrees and a tension of 50 g and 78 mm. Note that the contact between the magnetic layer and the sapphire blades was made once for a set of four sapphire blades.

Table 1 shows the measurement results of the number of dropouts, the number of instantaneous 1-] blockages, and the decrease in output.

Below all white Table 1 15μs; -18dB (times) (d
B) Example 1 10 pieces/min 1 to 3 -1 Comparative example 1150 pieces/min Many occurrences and -611 clogging also occurred 2 15 pieces/min 4 to 6-4 Note) In Table 1, the magnetic This means that instantaneous clogging occurred in the recording medium, and the number of times it occurred was large, so that it was not removed by the self-cleaning action of the magnetic head as the magnetic recording medium ran, making it impossible to measure the number of times it occurred.

4, f of rA! DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing an example of a rotating blade body of the present invention.

FIG. 2 is a perspective view showing an example of a blade provided on the outer circumferential portion of the rotating body shown in [-].

FIG. 3 is a side view of the rotary blade body shown in FIG. 1 above.

l: Rotating body, 2 parts of rotating body, 1 part, 3 blades

Claims (1)

[Claims] 1. A rotary blade body comprising a rotary body having a circular cross section and at least one blade provided on the outer periphery of the rotary body along its rotation axis. 2. The rotary blade body according to claim 1, wherein the number of blades provided on the outer circumference of the rotary body is within a range of 2 to 32. 3. A patent claim characterized in that the blade is made of a material selected from the group consisting of sapphire, alumina, cermet, zirconia, silicon nitride, silicon carbide, diamond, and cemented carbide. The rotating blade body according to item 1. 4. After smoothing the surface of a magnetic layer coated on a non-magnetic support and consisting of ferromagnetic powder dispersed in a binder, a rotating body with a circular cross section and a rotating body with a circular cross section are coated on the surface of the magnetic layer. A method for producing a magnetic recording medium, characterized in that grinding is carried out by bringing a rotary blade body, which is made up of at least one blade provided along the rotation axis of the rotary body, into contact with the outer periphery of the rotary body while rotating. 5. The method for manufacturing a magnetic recording medium according to claim 4, wherein the number of blades provided on the outer circumference of the rotating body is within a range of 2 to 32. 6. A patent claim characterized in that the blade is made of a material selected from the group consisting of sapphire, alumina, cermet, zirconia, silicon nitride, silicon carbide, diamond, and cemented carbide. A method for producing a magnetic recording medium according to item 4. 7. The method for manufacturing a magnetic recording medium according to claim 4, wherein the rotation speed of the rotary blade body is within a range of 100 to 6000 revolutions/minute. 8. Grinding the surface of the magnetic layer by bringing the magnetic layer into contact with the rotating blade while rotating the rotating blade in a direction opposite to the running direction of the magnetic layer while the magnetic layer is running. A method for manufacturing a magnetic recording medium according to claim 4, characterized in that: 9. The method for manufacturing a magnetic recording medium according to claim 4, wherein the surface of the magnetic layer is wiped off after the magnetic layer is ground.