JP2001216628A - Floppy disk and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a floppy disk having high dimensional stability and heat resistance. SOLUTION: A heat resistant resin films 4 each having a magnetic layer 3 consisting of a ferromagnetic metal thin film and a protective layer 9 which are formed thereon are thermally adhered onto both surfaces of a thermo plastic resin film 2 to manufacture the floppy disk and its method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a floppy disk having a high recording density, and more particularly, to a support having high dimensional stability and heat resistance, low warpage and a smooth surface, and a floppy using the support. The present invention relates to a disk and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a magnetic recording medium, as a method for forming a magnetic layer, a coating type magnetic recording medium in which a ferromagnetic powder is dispersed in a binder, a ferromagnetic metal thin film on a support by a sputtering method or the like. A magnetic recording medium composed of a ferromagnetic metal thin film manufactured by a vacuum film forming method such as an evaporation method is used. The ferromagnetic metal thin film formed by the vacuum film forming method can easily obtain high magnetic energy, and it is easy to make the surface of the magnetic layer smooth by smoothing the surface of the nonmagnetic substrate. It is suitable for a high-density recording material because it has a small spacing loss and high electromagnetic conversion characteristics. In particular, a magnetic layer obtained by a sputtering method can increase the magnetic energy as compared with a magnetic layer obtained by a vapor deposition method, and thus is used for a medium requiring a high recording density such as a hard disk.

On the other hand, floppy disk type magnetic recording media are widely used because of their superior impact resistance and low cost as compared with hard disks. Further, the present applicant has proposed a 3.5-type floppy disk 1 by using a coating type magnetic recording medium in which a thin magnetic layer is formed by applying a magnetic paint on a lower magnetic layer formed on a base or a lower non-magnetic layer. A large-capacity medium exceeding 100 MB per sheet is provided. However, its recording density is still 1/10 or less of that of a hard disk. This is largely due to the fact that although many attempts have been made to produce a magnetic layer by a sputtering method like a hard disk, it has not yet been put to practical use.

There are various reasons for this. One of the reasons is that it is difficult to develop a support suitable for such a floppy disk. The support of a floppy disk on which a magnetic layer is formed by a sputtering method is required to have at least the following four characteristics. (1) Smooth surface property When a magnetic recording medium is manufactured by a sputtering method, the surface property of the support is directly reflected on the surface property of the medium. A support having a smooth surface is required. Specifically, a support having a maximum surface roughness _Rmax of 60 nm or less is required. (2) High heat resistance The magnetic layer for high-density recording needs electromagnetic conversion characteristics such as high output and low noise. For this reason, when the magnetic layer is formed by sputtering, the film is formed while heating the support. Must. For this reason, the support is required to have extremely high heat resistance, and must be stable without causing deformation or chemical change even during heating. Specifically, the support must have heat resistance of 200 ° C. or higher.

(3) Less warpage In a high-density floppy disk, to increase the transfer speed,
While rotating at high speed like a hard disk, it slides at a very low flying height in contact with or close to the magnetic head. If the floppy disk runs out of surface, the floppy disk comes into strong contact with the head and the sliding becomes unstable, leading to deterioration in running durability and reliability. For this reason, it is necessary to keep the surface deviation of the floppy disk to 50 μm or less. Such run-out is strongly influenced by the static sled of the floppy disk. This warpage may be caused by a difference in stress between the front and back sides of the magnetic recording medium during the manufacturing process of the magnetic recording medium when the support originally has the warp. Although the warpage generated in the manufacturing process can be adjusted by the process conditions, the warpage inherent to the support is very difficult to adjust by the process conditions because the thickness of the support is much larger than the thickness of the magnetic layer. It is. In addition, when a polyimide or polyamide film having high heat resistance is used as the support, the material has high heat resistance, so that the shape cannot be corrected by heating. For this reason, it is necessary for the support to have almost no static warpage.
Specifically, it is necessary to press down to 1 mm or less in a state of being punched into a 3.5-type disk shape. (4) Dimensional stability Recent floppy disks are considered to be used inside notebook PCs due to the spread of notebook PCs. However, the temperature inside the notebook PC is high, and notebook PCs are carried around. They are often used over a wide temperature range. In such a situation, the floppy disk needs to have excellent dimensional stability with respect to temperature and be capable of stable tracking. For this purpose, the support must have excellent thermal dimensional stability.

It is very difficult to develop a support that satisfies the above four required properties, and it is not commercially available. For example, polyethylene terephthalate and polyethylene naphthalate, which are widely used as supports for magnetic tapes and floppy disks, have a glass transition temperature much lower than the heating temperature when forming a magnetic layer by a sputtering method. In many cases, deformation occurs when the layer is formed, and cracks often occur in the magnetic layer. When heated to such a temperature, the surface properties of the oligomer are significantly deteriorated due to the precipitation of the surface of the oligomer.

Although heat-resistant resin films such as aromatic polyimides and aromatic polyamides have sufficient heat resistance, it is difficult to realize smooth surface properties and low warpage due to problems in their production. Further, it is difficult to produce a polyamide film having a thickness of 50 μm or more. Further, polyimide and aramid films are expensive, and thus account for a large proportion of the manufacturing cost of the floppy disk to be manufactured. Further, no matter what kind of material is used, if the surface is smoothed to a certain degree or more, handling such as transporting and winding the support becomes very difficult. In order to solve this problem, it is necessary to intentionally create irregularities near the end surface of the support to prevent sticking to the conveying member or the back surface of the support, but even if this method is used, the width of the support may be reduced. If it is widened to some extent, the effect is reduced and the handling characteristics are deteriorated.

For this reason, in order to produce a support satisfying the above-mentioned required properties, it is necessary to process an existing film to improve the properties of the support. As such a method, a method in which a heat-resistant film such as a polyimide or a polyamide is laminated and attached to each other to produce a support made of a laminate can be considered. By using this method, even when the film is waiting for warpage, it is possible to greatly reduce the warpage by bonding the films in directions that cancel each other. Also, it is not always necessary for both surfaces to be smooth. One surface is made as smooth as possible, the other surface is roughened to facilitate handling, and the rough surfaces are bonded together to produce a support having both surfaces smooth. It is possible.

However, the conventional method of laminating using a general-purpose epoxy-based adhesive is insufficient in heat resistance of the adhesive. There was a problem that the temperature significantly decreased or volatile gas was generated by thermal decomposition. In the method of laminating using a thermosetting polyimide having sufficient heat resistance as an adhesive, the thermosetting polyimide is dissolved only in a specific high boiling point solvent, and it is difficult to completely remove this solvent. For this reason, there is a problem that air bubbles are generated on the bonding surface in the thermosetting process for bonding. Furthermore, when another thermosetting or thermoplastic resin having high heat resistance is applied by dissolving in a solvent and used as an adhesive, the viscosity of the adhesive is high, and it is not possible to remove foreign substances by precise filtration of the adhesive. Because it is possible,
There is a problem that foreign matter is easily mixed into the bonding surface.

For example, there has been proposed a method of bonding a heat-resistant polymer film having a magnetic layer formed thereon to a substrate film via an adhesive as disclosed in Japanese Patent Application Laid-Open No. Hei 8-249641. This requires a coating process for forming a film, and foreign matter is apt to be mixed into the adhesive surface, or the warpage of the base film affects the floppy disk, so that a floppy disk with little warping cannot be produced.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a floppy disk having smooth surface properties, high heat resistance, low warpage, and high dimensional stability.

[0012]

The object of the present invention is to provide a floppy disk with a heat-resistant resin film in which a magnetic layer made of a ferromagnetic metal thin film and a protective layer are formed on one side of a heat-resistant resin film. In addition, the problem is solved by a floppy disk which is heated and bonded so that the surface on which the magnetic layer is formed is on the outside. Further, in the above-mentioned floppy disk, the heat-resistant resin film is selected from an aromatic polyamide film and an aromatic polyimide film.

[0013] In the method of manufacturing a floppy disk, the heat-resistant resin film having the magnetic layer made of the ferromagnetic metal thin film and the protective layer may be formed such that the surfaces of the thermoplastic resin film having the magnetic layers formed on both sides are outside. This is a method for manufacturing a floppy disk in which a thermoplastic resin film and a heat-resistant resin film are bonded together by heating to form magnetic layers on both surfaces. Further, in the above-mentioned method for producing a floppy disk, at least one of the bonding surface of the heat-resistant resin film and the surface of the thermoplastic resin film is activated and then heat-bonded. The above-mentioned method for producing a floppy disk, wherein the heat bonding is performed by a flat plate hot press or a heat laminating roll at a temperature higher than the melting point of the thermoplastic resin film.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method of laminating a heat-resistant film having a magnetic layer formed on one side and having excellent surface smoothness on both sides of a thermoplastic resin film and heating and bonding the film. Excellent properties as a layer, surface properties,
In addition, it has been found that a magnetic recording medium excellent in warpage can be obtained.

FIG. 1 is a diagram for explaining a floppy disk of the present invention, and is a sectional view. In the floppy disk 1 of the present invention, a heat-resistant resin film 4 having a magnetic layer 3 is laminated on both surfaces of a thermoplastic resin film 2.
If the smoothness of the surface of the heat-resistant resin film 4 is insufficient, a magnetic layer having a smooth surface cannot be obtained. Therefore, the undercoat layer 5 may be formed on the heat-resistant resin film 4. An underlayer 6 is formed on the undercoat layer 5 for the purpose of improving the magnetostatic properties of the magnetic layer, and a magnetic layer 7 is formed thereon. Further, in order to control the crystal orientation of the underlayer 6, the seed layer 8 may be formed prior to the formation of the underlayer 6, and the purpose is to improve the adhesion between the underlayer 6 or the seed layer 8 and the undercoat layer 5. May form the adhesion layer 9. Further, a protective layer 10 and a lubricating layer 11 are formed on the magnetic layer 6. In the floppy disk 1 of the present invention, since the thermoplastic resin film 2 is used, the heat-resistant resin film 4 having the magnetic layer 3 formed on both surfaces thereof can be heat-bonded. Therefore, an adhesive is used for laminating the both. It can be stacked without any.

The heat-resistant resin film used in the present invention includes:
Aromatic polyimide film, aromatic polyamide film, polyetheretherketone, polyethersulfone, polyetherimide, polysulfone, polyphenylene sulfide, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), alkyl vinyl ether copolymer (PFA) And a heat-resistant resin film such as a fluororesin selected from tetrafluoroethylene-ethylene copolymer (ETFE) and chlorotrifluoroethylene resin (CTFE). Among these, a polyimide film and a polyamide film are preferable from the viewpoint of heat resistance. This is because the surface of the substrate reaches a high temperature due to the heating of the heat-resistant resin film used as the substrate when forming the magnetic layer by sputtering and the heat of the plasma during the formation, as described later. This causes problems such as release of decomposed gas and precipitation of oligomer.

The surface of the surface of the heat-resistant film which is to be the support is preferably as smooth as possible. This is because the surface property of the manufactured floppy disk has a very large effect on its electromagnetic conversion characteristics.
Specifically, when an undercoat layer described below is used, the surface roughness measured by an optical surface roughness meter is 10 nm or less, preferably 5 nm or less in center line average roughness Ra, and is measured by a stylus roughness meter. The measured protrusion height is within 1 μm, preferably 0.1 μm
Within. When the undercoat layer was not used, the surface roughness measured by an optical surface roughness meter was 3n in center line average roughness Ra.
m, preferably within 1 nm, and the projection height measured with a stylus-type roughness meter is within 0.1 μm, preferably 0.06 μm.
Within.

The adhesive surface of the heat-resistant resin film preferably has moderate unevenness for handling and adhesiveness. Specifically, the surface roughness measured by an optical surface roughness meter is the center line average roughness. Ra within 10 nm, preferably 5 n
Within 0.1 m, protrusion height measured with a stylus type roughness meter is 0.1 μm
Within, preferably within 0.06 μm. Further, in order to further increase the adhesive strength, it is preferable to use an activation treatment of the adhesive surface. For the activation, generally known corona treatment, oxygen plasma treatment, flame treatment, ultraviolet treatment, ozone treatment, chromic acid treatment and the like can be used. Among them, corona treatment and oxygen plasma treatment are preferred from the viewpoint of the effect of improving adhesive strength and productivity.

Examples of the polyimide film include Upilex manufactured by Ube Industries, Ltd., Apical manufactured by Kanebuchi Chemical Co., Ltd.
Examples include Kapton manufactured by Toray Dupont. Examples of the polyamide film include Aramica manufactured by Asahi Kasei Kogyo Co., Ltd. and Miktron manufactured by Toray Industries, Inc. The thickness of these heat resistant films is preferably in the range of 2 to 50 μm, particularly preferably 3 to 25 μm.

The thermoplastic resin film used in the present invention includes polyolefin, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyester, polyimide, polyether ether ketone, polyether sulfone, polyetherimide, polysulfone, polyphenylene sulfide, tetrafluoroethylene Thermoplastics such as fluororesins selected from ethylene-hexafluoropropylene copolymer (FEP), alkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), and chlorotrifluoroethylene resin (CTFE) Resin film can be used. Among them, those having a melting point in the range of 200 ° C to 300 ° C are preferable from the viewpoint of adhesiveness. If the melting point is higher than this, a high temperature is required for thermal bonding, and the productivity is reduced. Conversely, if the melting point is lower than this, the thermal stability of the floppy disk often decreases.

In selecting a heat-resistant resin film and a thermoplastic resin film, the following criteria are used. That is, in the present invention, in order to prevent the heat-resistant resin from adhering to the pressing member during the heat bonding, the melting point of the heat-resistant resin is higher than the heat bonding temperature, and the melting point of the thermoplastic resin is higher than the heat bonding temperature. Need to be low. Therefore, if a film is selected from such a viewpoint, for example, when bonding at 300 ° C., a combination using an aromatic polyimide for the heat-resistant resin film and polyether sulfone for the thermoplastic resin can be used. When bonding, use PF on heat-resistant resin
A can be used as a combination of A and polysulfone as a thermoplastic resin.

The thermoplastic resin film functions as an adhesive for the heat-resistant resin film, and the presence of the thermoplastic resin film on the support can reduce the warpage generated in the step of sputtering the magnetic layer. This is because even if warpage occurs in the heat-resistant resin film after the formation of the magnetic layer, the stress difference is caused by heating to a temperature equal to or higher than the glass transition point of the thermoplastic resin film during thermal bonding with the thermoplastic resin film. This is because it can be relaxed and fixed. In addition, it is possible to prevent warping in a specific direction due to the influence of temperature and humidity.

Since the thermoplastic resin film is used after being melt-bonded as described later, a general surface roughness can be used, but a smooth surface roughness is preferable. Specifically, the surface roughness measured by an optical surface roughness meter is within 10 nm, preferably within 5 nm as a center line average roughness Ra, and the projection height measured by a stylus roughness meter is 1 μm.
Within, preferably within 0.1 μm. This surface roughness is preferably substantially the same on the front and back surfaces.

The thermoplastic resin film of the present invention is preferably subjected to a surface activation treatment in order to increase the adhesive strength. For the activation of the surface, generally known corona treatment, oxygen plasma treatment, flame treatment, ultraviolet treatment, ozone treatment, chromic acid treatment and the like can be used. Among them, corona treatment and oxygen plasma treatment are preferred from the viewpoint of the effect of improving adhesive strength and productivity. The thickness of this thermoplastic film is 3 to
It is 75 μm, preferably 5 to 50 μm.

The thermal bonding is performed by laminating a thermoplastic resin film so that the surface of the heat-resistant resin film on which the magnetic layer is formed is on the outside, and bonding by heating. Heat lamination using a heat laminating roll, high frequency bonding, ultrasonic bonding, and the like can be used. Among them, heat lamination by a flat plate hot press or a heat laminating roll is preferable. The heating temperature at this time is determined by the temperature required for adhesion according to the characteristics of the film to be used, but is preferably at least the glass transition point of the thermoplastic resin film, more preferably stable adhesion by heating to the melting point or more It can be performed.

When a flat plate heat press is used, a heat-resistant resin film, a thermoplastic resin film, and a heat-resistant resin film may be stacked in this order, and may be heat-bonded one by one. And the whole may be heated by a heating means such as an oven to perform the bonding.
Although these methods are inferior in productivity, since the heat and stress distribution on the front and back surfaces can be made uniform, a support with less warpage can be manufactured.

In addition, it is possible to bond even a thermoplastic resin film having a high bonding temperature. At this time, the hot press is preferably performed in a vacuum in order to prevent generation of bubbles on the bonding surface and to prevent dust from adhering to each film. The surface roughness of the pressed surface is preferably smoother than that of the support to be used. If the surface is rough, the surface is transferred to the support and irregularities are formed on the surface of the support. Further, it is preferable that the press surface has been subjected to a surface treatment such as a fluorine process with a fluorine compound or the like in order to prevent the support body from sticking after bonding. Press pressure is 1 × 10 ^-2 〜1
MPa is preferred. The heating time depends on the thermal and chemical properties of the thermoplastic resin film, but can be appropriately selected from several seconds to several hours.

In the case of using heat lamination with a heat laminating roll, a heat-resistant resin film, a thermoplastic resin film, and a heat-resistant resin film may be stacked in this order and adhered one by one to a sheet. From the roll to the roll. When laminating in a single-wafer system, a film is superimposed on a smooth heating plate, and the upper or lower surface is pressed and bonded with a heat laminating roll, or the film is passed between the heat laminating rolls.
When laminating continuously, the film is adhered between the heat laminating rolls. The heating time at this time depends on the thermal and chemical properties of the thermoplastic resin film,
Within a few seconds.

For this reason, the surface temperature of the laminating roll needs to be set higher than the bonding temperature of the thermoplastic resin film. Heat laminating roll is steam heated,
Although heating by heating medium oil can be used, in the case of a thermoplastic resin film having a high bonding temperature, an induction heating roll may be used. The surface properties of the heat laminating roll are preferably smoother than the support used. If the surface is rough, the surface is transferred to the support and irregularities are formed on the surface of the support. Further, the lamination is preferably performed in a vacuum in order to prevent generation of air bubbles on the bonding surface and to prevent dust from adhering to each film. The laminating roll pressure is suitably from 10 N / m to 10 kN / m.

Next, the undercoat layer that can be used in the present invention will be described. When the surface properties of the heat-resistant resin film of the present invention are insufficient, it is preferable to form an undercoat layer on the surface of the heat-resistant resin film for the purpose of smoothing. Since the undercoat layer is required to have heat resistance in the same manner as the heat-resistant resin film, it is necessary to use a polyimide resin, a polyamide-imide resin, a silicone resin, a fluororesin or the like, and a polyester resin or the like cannot be used because of its poor heat resistance. Above all, it is preferable to use a thermosetting imide or a thermosetting silicone resin having a high smoothing effect as a material of the undercoat layer. The thickness of the undercoat layer is preferably 0.1 to 3 μm. The undercoat layer may be formed before or after bonding the heat-resistant resin film and the thermoplastic resin film.

Examples of the use of a thermosetting imide resin used as a substance for forming an undercoat layer include a polyimide resin which is a thermal polymer of an imide monomer having two or more terminal unsaturated groups in a molecule. An example of such an imide monomer is bisallylnadiimide represented by the following chemical formula 1.

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However, R ¹ and R ² are independently selected hydrogen or methyl groups, and R ³ is a divalent linking group such as an aliphatic or aromatic hydrocarbon group. That is, the thermosetting polyimide resin that is preferable as the base layer of the present invention is not a polyimide resin that has already been polymerized, but is a polyimide that is formed by first forming a coating film of an imide monomer on a heat-resistant resin film and then thermally polymerizing it.

This imide monomer has already undergone the imide cyclization reaction and has two or more terminal unsaturated groups in the molecule. The polymerization reaction on the polyimide proceeds by addition polymerization of the vinyl group by heating or the like. Therefore, since the polymerization reaction proceeds at a relatively low temperature, it can be formed as an underlayer on various non-magnetic supports including polyimide. Further, the imide monomer can be dissolved in a general-purpose organic solvent depending on its structure, and thus is excellent in productivity and workability. In addition, since the imide monomer has a smaller molecular weight than polyimide, the viscosity of the solution is low, and when this is applied on a non-magnetic support,
Good wraparound for unevenness and high smoothing effect.

An imide monomer compound having such an imide ring and two or more terminal unsaturated bonds is disclosed in JP-A-59-806.
No. 62, JP-A-60-178882, JP-A-61-18761, JP-A-63-170358, and JP-A-7-53516. Known compounds described above can be used. In compound 1, R ¹ and R ² are independently selected hydrogen or a methyl group, and R ³ can be any one of divalent linking groups such as aliphatic and aromatic. For example, a linear or branched alkylene group and alkenyl group, a cycloalkylene group, a cycloalkylene group having an alkylene group, an aromatic group, an aromatic group having an alkylene group, a polyoxyalkylene group, a carbonyl group, an ether group, and the like. No.

The solvent solubility of the imide monomer and the heat resistance of the polyimide resin, which is a polymer thereof, are determined mainly by the structure of R ³ . Thus the desired characteristics are achieved by selecting the structure of R ^3. As such compounds, those commercially available from Maruzen Petrochemical Co., Ltd. as BANI series and ANI series can be used.

The undercoat layer of the present invention may contain components other than imide monomers. For example, a curing agent for accelerating polymerization, heat-resistant fine particles (filler) for forming irregularities on the surface, a coupling agent for improving adhesion, a rust inhibitor for preventing oxidation of the magnetic layer, and the like are included. As a curing agent, p-toluenesulfonic acid, p-xylenesulfonic acid, methyl toluenesulfonate, pyridinium-p-toluenesulfonate, pyridinium-m-
Nitrobenzenesulfonate, methylhydrazine sulfate and the like can be used. The coating solvent varies depending on the type of R ^{3 in} Chemical Formula 1, but in many structures it can be dissolved in toluene, xylene, acetonitrile, cyclohexanone, methyl ethyl ketone, acetone, etc., and in some structures it is isopropyl alcohol, ethanol, methanol, etc. Can also be dissolved. These mixed solvents can be used as the solvent.

As a preferred example of the thermosetting silicone resin in the present invention, a silicone resin prepared by a sol-gel method using a Keitan compound into which an organic group has been introduced as a raw material can be given. Such a silicone resin has a structure in which a part of the bond of silicon dioxide is substituted with an organic group, and has much higher heat resistance than silicone rubber. Further, since it is more flexible than a silicon dioxide film, cracking and peeling hardly occur even when it is formed on a flexible film such as a heat-resistant resin film.

Since the method is a method in which a monomer as a raw material is directly applied on a heat-resistant resin film and cured, a general-purpose solvent can be used, and the wraparound to unevenness is good.
High smoothing effect. Furthermore, since the condensation polymerization reaction proceeds from a relatively low temperature by the addition of a catalyst such as an acid or a chelating agent, curing can be performed in a short time, and therefore, it can be produced by a general-purpose coating machine.

The monomer used as a raw material of the thermosetting silicone resin is a silane coupling agent having an organic residue such as an organic residue containing an aromatic hydrocarbon group, an aliphatic group or an epoxy group. Aromatic hydrocarbon groups and aliphatic hydrocarbon groups have the effect of imparting flexibility to the cured resin, and silane coupling agents having aromatic hydrocarbon groups are more heat-resistant than those having aliphatic hydrocarbon groups introduced. It is preferable because of excellent properties. Further, the silane coupling agent containing an epoxy group has an effect of curing the coating film from a relatively low temperature. For example, a silane coupling agent containing an aromatic hydrocarbon group is a compound having a structure represented by the following chemical formula 2.

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Wherein R and R 'are monovalent organic groups such as a methyl group; A is a divalent organic group such as a direct bond or an alkylene group;
B is a monovalent group x + y + z = 4 such as an alkoxy group, a halogen, and a hydroxyl group. In Chemical Formula 2, A is preferably absent, that is, directly connected or a methylene group. B is preferably an alkoxy group in consideration of reactivity and corrosiveness to the magnetic layer,
In order to facilitate the polymerization reaction, an alkoxy group having 4 or less carbon atoms such as a methoxy group is particularly preferable. x is preferably 1 or 2, but is particularly preferably 1 in order to facilitate the polymerization reaction. y is preferably 0 or 1, but particularly preferably 0 for facilitating the polymerization reaction. Accordingly, z is particularly preferably 3. Examples of such specific examples include the following.

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The silane coupling agent containing an organic residue having an epoxy group has, for example, a structure represented by the following chemical formula 3.

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A is a divalent organic residue such as an alkylene group B is a monovalent organic residue such as hydrogen or an alkyl group R is a monovalent organic residue such as an alkyl group X is an alkoxy group, a hydroxyl group, a halogen , A monovalent group selected from hydrogen, i + j + k = 4. In the structure of Formula 3, A is preferably hydrogen. R is a monovalent organic residue such as a methyl group or an ethyl group. X is preferably an alkoxy group in consideration of the reactivity and the influence on the corrosion of the magnetic layer. In order to facilitate the polymerization reaction, X is particularly preferably an alkoxy group having 4 or less carbon atoms such as a methoxy group. i is preferably 1 or 2, but is preferably 1 in order to facilitate the polymerization reaction. j is preferably 0 or 1, but particularly preferably 0 for facilitating the polymerization reaction. Therefore, k is particularly preferably 3. Examples of such a compound include those represented by the following chemical formula. These compounds are disclosed in JP-A-51-111871 and JP-A-61-18771.
It is described in JP-A-3-23224.

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For heat resistance, cost reduction, and polymerization rate adjustment, a silane coupling agent containing a hydrocarbon group such as a methyl group may be mixed and used. When a silane coupling agent containing a hydrocarbon is used in combination, the heat resistance of the undercoat layer can be improved. Specifically, this silane coupling agent containing a hydrocarbon group has the following structure. R—Si (OR ′) ₃ where R and R ′ are a hydrocarbon group, and the smaller the carbon number of R, the more effective the improvement of the heat resistance of the undercoat layer. The silane coupling agent having an aromatic hydrocarbon group and the silane coupling agent containing an organic residue having an epoxy group, such as alkoxysilane, are hydrolyzed and polymerized by coating and drying by the method described below to form a siloxane. Create a bond. On the other hand, the epoxy group undergoes ring opening polymerization by an acid catalyst or heat. The hydrolysis rate and the polymerization rate can be adjusted by adding an acid such as hydrochloric acid.

In order to start the polymerization from a lower temperature,
It is preferable to use a curing agent in combination, for example, a metal chelate compound,
Various compounds such as organic acids and salts thereof, and perchlorates are known, but a metal chelate compound is particularly preferred as a curing agent from the viewpoint of lowering the curing temperature and preventing corrosion of the magnetic layer. For example, when aluminum acetylacetonate is added to 3-glycidoxypropyltrimethoxysilane as a curing catalyst, curing can be performed only by heating at about 100 ° C. for a short time. Therefore, the film can be wound without blocking by using the gravure continuous coating method. As such a curing agent, a chelate compound of a metal with a β-diketone such as aluminum acetylacetonate, zirconium acetylacetonate, or titanium acetylacetonate is particularly effective. The coating solvent used at this time is determined by the amount of hydrochloric acid added and the structure of the silane coupling agent, but ethanol, methanol, isopropyl alcohol, cyclohexanone and the like can be used.

In the present invention, a method for preparing an undercoat layer comprising the above-mentioned thermosetting polyimide resin layer or thermosetting silicone resin layer on a heat-resistant resin film includes adding a monomer as a raw material and a curing agent if necessary. , A coating solution dissolved in an organic solvent, a wire bar method, a gravure method,
A method of applying the composition on a heat-resistant resin film by a method such as a spray method, a dip coating method, and a spin coating method and then drying the applied film can be used. Further, thereafter, the undercoat layer may be baked, if necessary, to accelerate the curing and improve heat resistance, solvent resistance, adhesion, and the like. Drying is performed to evaporate the solvent, but curing can be performed at this time. As a drying method, hot air drying, infrared drying and the like which are generally performed can be used. The drying temperature at this time is preferably about 60 ° C to 250 ° C.

After the coating film is dried, as a firing method for further accelerating the curing, hot air heating, infrared heating, hot roller heating and the like can be used. The heating temperature at this time depends on the thickness of the coating film, the method of forming the magnetic layer afterward, and the film forming temperature, but in the case of about 1 μm, it is in the range of 100 to 350 ° C., preferably 200 to 270 ° C. It is. If the temperature is lower than this, the progress of the polymerization reaction may be insufficient, or a residual gas or a decomposition gas may be generated during the sputtering of the magnetic layer, which may hinder the crystal growth of the magnetic layer. Conversely, if it is too high, the support may be deformed or productivity may be reduced. For some materials, polymerization by ultraviolet irradiation, electron beam irradiation, or the like is also possible in addition to polymerization by heating.

Further, by providing minute projections having a very low height on the surface of the undercoat layer, the real contact area between the magnetic recording medium and the sliding member can be reduced and the sliding characteristics can be improved. It is particularly preferable that the upper magnetic layer surface has a fine projection structure. This microprojection structure has the effect of significantly improving the handleability of the support after bonding. As a method of producing such a fine projection structure, a method of applying spherical silica particles, a method of applying an emulsion to form organic projections, and the like can be used, but silica particles are preferable in order to ensure heat resistance.

It is also possible to use a binder to fix the projections to the film surface, but a resin having sufficient heat resistance is preferable in order to secure heat resistance. It is particularly preferable to use a thermosetting imide or a thermosetting silicone resin used for forming a layer. The height of the microprojections is 5 to 60 nm, preferably 10 to 30 nm, and the density is 0.1 to 100.
Particles / μm ² , preferably 1 to 10 particles / μm ² . If the height of the minute projections is too high, the electromagnetic conversion characteristics are degraded due to the spacing loss between the recording / reproducing head and the medium. If the height of the minute projections is too low, the effect of improving the sliding characteristics is reduced. If the density of the fine projections is too low, the effect of improving the sliding characteristics is reduced, and if it is too high, the number of high projections increases due to the increase in aggregated particles, and the electromagnetic conversion characteristics deteriorate. The coating thickness of the binder is 20 nm or less. If the binder is too thick, it may adhere (block) to the back surface of the film after drying.

The ferromagnetic metal thin film serving as a magnetic layer in the floppy disk of the present invention is formed by a sputtering method or a vacuum evaporation method. Examples of the composition of the magnetic layer include metals or alloys mainly containing cobalt.
o-Cr, Co-Ni-Cr, Co-Cr-Ta, Co
-Cr-Pt, Co-Cr-Ta-Pt, Co-Cr-
Pt-Si, Co-Cr-Pt-B, Co-O or the like can be used. In particular, Co-Cr is used to improve electromagnetic conversion characteristics.
-Pt and Co-Cr-Pt-Ta are preferred. It is desirable that the thickness of the magnetic layer be 10 to 30 nm.

In this case, it is preferable to provide an underlayer for improving the magnetostatic characteristics of the magnetic layer. The composition of the underlayer may be a metal or an alloy. Specifically, Cr, V, Ti, Ta, W, Si or the like or an alloy thereof can be used, and among them, Cr and Cr-Ti are particularly preferable. The thickness of the underlayer is 5 nm to 50 nm, preferably 10 nm to 30 nm.

In order to further control the crystal orientation of the underlayer, it is preferable to use a seed layer under the underlayer. Specifically, Ta, Mo, W, V, Zr, Cr, Rh, H
f, Nb, Mn, Ni, Al, Ru, Ti or an alloy thereof, particularly preferably Ta, Ni-P, Ni-Al,
It is selected from Cr-Ti, and preferably has a thickness of 15 to 60 nm. Also, these are different from the underlayer,
It is used in a state where the crystallite is smaller than that of the amorphous layer or the underlayer.

Further, an adhesion layer may be formed in order to enhance the adhesion between the undercoat layer and the seed layer. If the seed layer is not formed, the adhesion between the undercoat layer and the underlayer may be increased. An adhesion layer may be introduced. As the adhesion layer, specifically, Cr, V, Ti, Ta, W, Si, or the like or an alloy thereof can be used. When the magnetic layer is formed by a sputtering method, it is preferable to form a film while the support is heated, and it is preferable to use a DC or RF magnetron sputtering method and set the temperature of the support to 100 ° C. to 250 ° C.

On the other hand, the temperature of the support is not only heated but also heated by sputtering. In addition, both the sputtering method and the vacuum deposition method can be used, either a single-wafer type film forming method for forming a film one by one or a web film forming method for continuously forming a film on a web-like film. When performance is important, a single-wafer type film forming method is preferable, and when productivity is important, a web film forming method is preferable. In particular, when the present invention is used in the web film forming method, the productivity can be significantly improved. This is because the formation of the magnetic layer only needs to be performed on one side in the web film formation method. This is because surface defects can be significantly reduced, and continuous lamination using a hot laminator roll can be performed for bonding.

In the floppy disk of the present invention, it is preferable to provide a protective layer on the ferromagnetic metal thin film. With this protective layer, running durability and corrosion resistance can be remarkably improved. As the protective layer, silica, alumina, titania, zirconia, cobalt oxide, oxides such as nickel oxide, nitrides such as titanium nitride, silicon nitride, boron nitride, silicon carbide, chromium carbide, carbides such as boron carbide,
Examples of the protective layer include carbon such as graphite and amorphous carbon. As this protective layer, a hard film having a hardness equal to or higher than that of the head material is preferable, and further, a material that hardly causes seizure during sliding and has a stable and stable effect is most preferable. Examples include a hard carbon film called diamond-like carbon (DLC).

The diamond-like carbon film is formed by plasma CVD.
Law, an amorphous carbon film produced by sputtering, cluster and Sp by microscopically Sp ² bond
It is a mixture of clusters by ^three bonds. The hardness of this film is 10 × 10 ³ MPa to 20 × 10 ^{3 in} Vickers hardness.
MPa or more. When measured by Raman spectroscopy of the diamond-like carbon film, a main peak called a G peak at about 1540 ^-1 cm was 139.
This can be confirmed by detecting a so-called D peak at 0 cm ^-1 . These diamond-like carbon films can be prepared by a sputtering method or a CVD method. However, since the productivity, the stability of quality, and the excellent abrasion resistance can be ensured even with an ultrathin film having a thickness of 10 nm or less, the CVD method is used. It is preferable to produce the methane, ethane,
Negative bias voltage is applied to the magnetic layer or a reticulated electrode provided in front of the magnetic layer by decomposing a carbon-containing compound such as an alkane such as propane or butane, an alkene such as ethylene or propylene, or an alkyne such as acetylene. It is preferable to apply the pressure and accelerate the deposition. Further, by mixing nitrogen gas with the source gas to form a diamond-like carbon film made of C, H, and N, the friction coefficient with respect to the head can be reduced. When the thickness of the hard carbon protective layer is large, the electromagnetic conversion characteristics deteriorate and the adhesion to the magnetic layer decreases,
When the film thickness is small, abrasion resistance is insufficient.
nm, particularly preferably 5 to 20 nm.

In the floppy disk of the present invention, in order to improve running durability and corrosion resistance, it is preferable to provide a lubricant or a rust inhibitor on the magnetic layer or the protective layer. As the lubricant, known hydrocarbon-based lubricants, fluorine-based lubricants, extreme pressure additives and the like can be used. Examples of the hydrocarbon-based lubricant include carboxylic acids such as stearic acid and oleic acid, esters such as butyl stearate, sulfonic acids such as octadecylsulfonic acid, phosphoric esters such as monooctadecyl phosphate, stearyl alcohol, oleyl alcohol and the like. Alcohols, carboxylic acid amides such as stearic acid amide, and amines such as stearylamine.

Examples of the fluorine-based lubricant include lubricants in which part or all of the alkyl group of the hydrocarbon-based lubricant is substituted with a fluoroalkyl group or a perfluoropolyether group. Examples of the perfluoropolyether group include a perfluoromethylene oxide polymer, a perfluoroethylene oxide polymer, a perfluoro-n-propylene oxide polymer (CF ₂ CF ₂ CF ₂ O) _n , and a perfluoroisopropylene oxide polymer (CF ( CF ₃ ) CF
₂ O) _n or a copolymer thereof. Specifically, a perfluoromethylene-perfluoroethylene copolymer having a hydroxyl group at a molecular weight terminal (FODI manufactured by Audimont Co., Ltd.)
MBLIN Z-DOL).

Examples of extreme pressure additives include phosphoric esters such as trilauryl phosphate, phosphites such as trilauryl phosphite, thiophosphites and thiophosphoric esters such as trilauryl trithiophosphite, and the like. And sulfur-based extreme pressure agents such as dibenzyl sulfide.

The above lubricants may be used alone or in combination.
used. Apply these lubricants on the magnetic layer or protective layer.
As a method of imparting water to a lubricant, a lubricant is dissolved in an organic solvent
Ear bar method, gravure method, spin coating method, dip
Apply by a coating method or adhere by vacuum evaporation.
Just do it. The amount of lubricant to be applied is 1 to 30 mg / m ^Two
Is preferably 2 to 20 mg / m^TwoIs particularly preferred.

The rust preventives usable in the present invention include nitrogen-containing heterocycles such as benzotriazole, benzimidazole, purine and pyrimidine, and derivatives having an alkyl side chain introduced into their mother nucleus, benzothiazole, 2-mercapto And nitrogen- and sulfur-containing heterocycles such as benzothiazole, tetrazaindene ring compounds and thiouracil compounds, and derivatives thereof.

These may be mixed with a lubricant and applied on the protective layer, or may be applied on the protective layer before applying the lubricant, and the lubricant may be applied thereon. The coating amount of the rust inhibitor is preferably 0.1 to 10 mg / m ² , and 0.5 to 10 mg / m ^2.
5 mg / m ² is particularly preferred. Tetrasignedene ring compounds usable for such purposes include those shown below.

◎

Embedded image

Here, R is a hydrocarbon group selected from an alkyl group, an alkoxy group and an alkylamide group.
Particularly preferably not having 3 to 20 carbon atoms, R ⁴ OCOCH ₂ in the case of alkoxy - R ⁴ s, C ₃ H
_{7 -, C 6 H 13 -} , phenyl, also in the case of alkyl _{groups, C 6 H 13 -, C} 9 H 19 -, C 17 H 35 - , and the like, in the case of an alkylamide R ⁵ NHCOCH ₂ - the R ⁵ phenyl, C ₃ H ₇ - and the like. Further, examples of the thiouracil ring compound include the following.

◎

Embedded image

Here, R is selected from the same as those in the above-mentioned tetrazaindene ring compound.

[0071]

The present invention will be described below with reference to examples. Example 1 Both surfaces are corona-treated and the maximum protrusion roughness R of the magnetic surface is
_max is 0.1 μm, center line average roughness Ra is 1.2 nm,
Aromatic polyamide film having a thickness of 12 μm is formed with a diameter of 18c.
m, and a thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co.) is spin-coated on the magnetic surface.
Of a cyclohexane / ethanol mixed solvent (1: 1) was applied and dried at room temperature.
After heating for an hour, an undercoat layer having a thickness of 1.0 μm was prepared. Further, a cyclohexanone solution of silica particles having a diameter of 25 nm and a thermosetting imide resin was applied thereon,
After drying at 1 ° C. for 1 hour, microprojections having an average projection height of 20 nm and a projection density of 3 / μm ² were formed.

Next, this film was sandwiched and fixed in a circular holder to which a uniform tension was applied, and the film was placed in a sputtering apparatus for forming a magnetic layer. After the support was heated to 200 ° C., the Cr—Cr film was formed by DC magnetron sputtering. T
i An underlayer is formed to a thickness of 30 nm, and further Co-Cr
-A 30 nm thick Pt magnetic layer was formed. Further, this sample was taken out from the sputtering apparatus, and a 15-nm-thick diamond-like carbon protective layer was formed on the magnetic layer by a plasma CVD method using ethane as a raw material.

Next, both sides of the adhesive surface of this film were subjected to corona treatment, and the center line average roughness Ra was 4.1 nm.
A circular polyetherimide film of 4.5 nm, thickness of 25 μm and diameter of 12 cm is superimposed on both sides, and this is made into one set.
A pressure of 981 Pa was applied between stainless steel plates having a diameter of 98 cm and pressed. In this state, it was taken out into the atmosphere, placed in an oven, and heated at 260 ° C. for 5 hours. Thereafter, the film was taken out.

Further, on the protective layer of this sample, a perfluoropolyether-based lubricant (FOMBLI manufactured by Ausimont) was used.
NZ-DOL) with a fluorinated solvent (Sumitomo 3M F
The solution dissolved in C-77) was applied by a dip coating method to form a lubricating layer having a thickness of 1 nm. Then, this sample was punched into a 3.5-type magnetic disk to produce a floppy disk FD1. The obtained floppy disk FD1 was evaluated by the following evaluation methods, and the results are shown in Table 1.

Example 2 Both surfaces were corona-treated, and the maximum protrusion roughness R of the magnetic surface was
_max is 0.2 μm, center line average roughness Ra is 2.0 nm,
An aromatic polyimide film having a thickness of 25 μm and a diameter of 18c
m, and a thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co.) is spin-coated on the magnetic surface.
Of a cyclohexane / ethanol mixed solvent (1: 1) was applied and dried at room temperature.
Heating was performed for a time to prepare an undercoat layer having a thickness of 1.7 μm. Further, a cyclohexanone solution of silica particles having a diameter of 25 nm and a thermosetting imide resin was applied thereon,
At 1 ° C. for 1 hour, the average value of the protrusion height is about 20 nm,
Fine projections having a projection density of 3 / μm ² were formed.

Next, this film was sandwiched and fixed in a circular holder to which a uniform tension was applied, and the film was placed in a sputtering apparatus for forming a magnetic layer. After the support was heated to 200 ° C., the Cr— T
i An underlayer is formed to a thickness of 30 nm, and further Co-Cr
-A 30 nm thick Pt magnetic layer was formed. The underlayer and the magnetic layer were formed on both surfaces of the support. Further, this sample was taken out from the sputtering apparatus, and a thickness of 15 nm was formed on the magnetic layer by plasma CVD using ethane as a raw material.
A diamond-like carbon protective layer was formed.

Next, the adhesive surface of this film is corona-treated on both sides, and the center line average roughness Ra is 5.
5 nm, the other surface is 5.6 nm, and the thickness is 25 μm, and is 12 cm in diameter. It is superimposed on both surfaces of a circular film made of tetrafluoroethylene-ethylene copolymer (ETFE). A pressure of 981 Pa was applied between stainless steel plates having a diameter of 20 cm and mirror-polished in a vacuum, and pressed. In this state, it was taken out into the atmosphere, placed in an oven, and heated at 260 ° C. for 5 hours. afterwards,
This film was taken out.

Further, a perfluoropolyether-based lubricant (FOMBLI manufactured by Ausimont Co., Ltd.) was applied on the protective layer of this sample.
NZ-DOL) with a fluorinated solvent (Sumitomo 3M F
The solution dissolved in C-77) was applied by a dip coating method to form a lubricating layer having a thickness of 1 nm. Then, this sample was punched into a 3.5-type magnetic disk to produce a floppy disk FD2. The obtained floppy disks were evaluated by the following evaluation methods, and the results were shown in Table 1.
Shown in

Example 3 Both surfaces are corona-treated and the maximum protrusion roughness R of the magnetic surface is
_max is 0.1 μm, center line average roughness Ra is 1.2 nm,
A roll-shaped aromatic polyamide film having a thickness of 25 μm and a width of 30 cm is set on a continuous winding type gravure coater, and a coating solution having the following composition is applied by a gravure coating method, which is dried and cured at 120 ° C. An undercoat layer having a thickness of 0.6 μm was prepared from the silicone resin and wound up. Further, on this undercoat layer, silica particles having a diameter of 25 nm and an ethanol / cyclohexanone solution (1: 1) of the following thermosetting silicone resin were applied, and then dried at 120 ° C. to obtain an average projection height of 20 nm. The density is 3 pieces /
A microprojection of μm ² was formed. 170 ° C
0.1m / sec while contacting the heated roll
, And the undercoat layer was cured and wound up.

3-glycidoxypropyltrimethoxysilane 20.0% by weight Phenyltriethoxysilane 20.0% by weight Ethanol 44.6% by weight Cyclohexanone 0.6% by weight Purified water 10.0% by weight Hydrochloric acid (1 mol / l) 4.4% by weight Aluminum acetylacetonate 0.4% by weight The heat-resistant resin film provided with the undercoat layer was set in a continuous winding type sputtering apparatus, and the speed was 60 cm / mi.
While being transported with n, a DC magnetron sputtering method was applied to the film magnetic surface on a heating roll heated to 150 ° C. so that the Cr-Ti underlayer was 30 nm, the Co-Cr-Pt magnetic layer was 30 nm, and the carbon protective layer was 20 nm. And wound up.

Next, two rolls of the heat-resistant resin film provided with the magnetic layer and one roll of the polyethersulfone film used as a heating adhesive member were placed on a continuous heat laminator. This polyethersulfone film is corona-treated on both sides, has a center line average roughness Ra of 4.1 nm on one side, 4.9 nm on the other side, and a thickness of 25 μm.
m and a width of 25 cm were used. Overlay these, 300
A linear pressure of 4.91 N / m was applied to the laminating roll heated to 0 ° C., and the laminate was conveyed at a speed of 0.1 m / sec to perform heat bonding.

Next, this sample was attached to a continuous gravure coater, and a perfluoropolyether-based lubricant (FOMBLINZ-DO manufactured by Ausimont) was applied on the protective layers on both sides.
L) with a fluorinated solvent (FC-77 manufactured by Sumitomo 3M Limited)
Solution is applied by dip coating method and the thickness is 1n
m of lubricating layer was prepared and wound. Then, this sample was punched into a 3.5-type magnetic disk to produce a floppy disk FD3. The obtained floppy disks were evaluated by the following evaluation methods, and the results were shown in Table 1.
Shown in

Comparative Example 1 Both surfaces were corona-treated, and the maximum protrusion roughness R of the magnetic surface was
_max is 0.1 μm, center line average roughness Ra is 1.2 nm,
Aromatic polyamide film having a thickness of 12 μm was formed with a diameter of 18c.
m, and a thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co.) is spin-coated on the magnetic surface.
Of a cyclohexane / ethanol mixed solvent (1: 1) was applied and dried at room temperature.
After heating for an hour, an undercoat layer having a thickness of 1.0 μm was prepared. Further, a cyclohexanone solution of silica particles having an average diameter of 25 nm and a thermosetting imide resin was applied thereon,
After drying at 50 ° C. for 1 hour, the average height of the protrusions is 20 n.
m, microprojections having a projection density of 3 / μm ² were formed.

Next, this film was sandwiched and fixed in a circular holder to which a uniform tension was applied, attached to a sputtering device for forming a magnetic layer, and the support was heated to 200 ° C., and then Cr—Cr was deposited by DC magnetron sputtering.
A Ti underlayer is formed to a thickness of 30 nm, followed by Co-C
An r-Pt magnetic layer was formed to a thickness of 30 nm. Further, this sample was taken out from the sputtering apparatus, and a 15-nm-thick diamond-like carbon protective layer was formed on the magnetic layer by a plasma CVD method using ethane as a raw material. Next, a polester resin (Toyobo Byron # 10) is applied to the adhesive surface of this film.
The adhesive layer was prepared by applying the methyl ethyl ketone solution of 0) by a spray coat method.

The adhesive surface of this film is corona-treated on both sides, and the center line average roughness Ra is 2.2 n on one side.
m, the other surface is 2.5 nm, thickness 25 μm, diameter 12c
m on both sides of a circular polyethylene terephthalate,
Ten sets of these were stacked and pressed in vacuum while applying a pressure of 981 Pa between mirror-polished stainless steel plates having a diameter of 20 cm. In this state, it was taken out into the atmosphere, placed in an oven, and heated at 100 ° C. for 5 hours. Thereafter, the film was taken out.

Further, a perfluoropolyether-based lubricant (FOMBLI manufactured by Ausimont Co., Ltd.) was applied on the protective layer of this sample.
NZ-DOL) with a fluorinated solvent (Sumitomo 3M F
The solution dissolved in C-77) was applied by a dip coating method to form a lubricating layer having a thickness of 1 nm. Then, this sample was punched into a 3.5-type magnetic disk to produce a floppy disk FD4. The obtained floppy disks were evaluated by the following evaluation methods, and the results were shown in Table 1.
Shown in

[0087] Comparative Example 2 the maximum protrusion roughness R _max is 0.1μm smooth surface, the center line average roughness Ra 1.2 nm, the rough surface R _max is 0.2 [mu] m, R
The support 5A is a circular aromatic polyamide film having the same chemical structure as in Example 1 having a diameter of 1.8 nm, a thickness of 50 μm, and a diameter of 18 cm, and a thermosetting imide resin (Maruzen Petrochemical Co., Ltd.) is provided on the surface of the support 5A. A solution of BANI-NB) in cyclohexane / ethanol mixed solvent (1: 1) was applied by dip coating and dried at room temperature.
The coating was heated at 50 ° C. for 3 hours to form an undercoat layer having a thickness of 1.0 μm. Furthermore, a silica particle having an average diameter of 25 nm and a cyclohexanone solution of a thermosetting imide resin are applied thereon, followed by drying at 250 ° C. for 1 hour to obtain an average projection height of 20 nm and a projection density of 3 / μm. ^Two microprojections were formed. This was designated as support 5B.

Next, the support 5B was cut out, sandwiched and fixed in a circular holder to which a uniform tension was applied, and set in a sputtering apparatus for forming a magnetic layer.
After heating to 00 ° C., a 30 nm Cr-Ti underlayer was formed by DC magnetron sputtering, followed by a 30 nm Co-Cr-Pt magnetic layer. The underlayer and the magnetic layer were formed on both sides of the support. Further, this sample was taken out from the sputtering apparatus, and the thickness of the magnetic layer was reduced to 1 by a plasma CVD method using ethane as a raw material.
A 5 nm diamond-like carbon protective layer was formed. Next, the sample was taken out of the holder, and a perfluoropolyether-based lubricant (FOM manufactured by Ausimont, Inc.) was placed on the protective layer.
A solution of BLINZ-DOL in a fluorine-based solvent (FC-77 manufactured by Sumitomo 3M Limited) was applied by a dip coating method to form a lubricating layer having a thickness of 1 nm. Then, the sample was punched into a 3.5-type magnetic disk to produce a floppy disk. The obtained floppy disk was designated as FD5. The obtained floppy disks were evaluated by the following evaluation methods, and the results are shown in Table 1.

[0089] Comparative Example 3 the maximum protrusion roughness R _max is 0.2 [mu] m of the smooth surface, the center line average roughness Ra 2.0 nm, the rough surface R _max is 0.2 [mu] m, R
a is a circular aromatic polyimide film having a thickness of 2.9 μm, a thickness of 50 μm, and a diameter of 18 cm as a support 7A, and then a cyclohexane of a thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co.) is provided on the surface of the support. A solution dissolved in a mixed solvent of ethanol / ethanol (1: 1) was applied by a dip coating method, dried at room temperature, and then heated at 250 ° C. for 3 hours to form a 1.7 μm-thick undercoat layer. Further on this,
After applying a cyclohexanone solution of silica particles having a diameter of 25 nm and a thermosetting imide resin, the coating is dried at 250 ° C. for 1 hour to form fine projections having an average projection height of 20 nm and a projection density of 3 / μm ^2. Formed. This was designated as support 7B.

Next, the support 7B was cut out, sandwiched and fixed in a circular holder to which a uniform tension was applied, and set in a sputtering apparatus for forming a magnetic layer.
After heating to 00 ° C., a 30 nm Cr-Ti underlayer was formed by DC magnetron sputtering, followed by a 30 nm Co-Cr-Pt magnetic layer. The underlayer and the magnetic layer were formed on both sides of the support. Further, this sample was taken out from the sputtering apparatus, and the thickness of the magnetic layer was reduced to 1 by a plasma CVD method using ethane as a raw material.
A 5 nm diamond-like carbon protective layer was formed. Next, the sample was taken out of the holder, and a perfluoropolyether-based lubricant (FOI, manufactured by Audimont Corporation) was placed on the protective layer.
A solution in which MBLINZ-DOL was dissolved in a fluorine-based solvent (FC-77 manufactured by Sumitomo 3M Limited) was applied by a dip coating method to form a lubricating layer having a thickness of 1 nm. Then, the sample was punched into a 3.5-type magnetic disk to produce a floppy disk. The obtained floppy disk was designated as FD6. The obtained floppy disks were evaluated by the following evaluation methods, and the results are shown in Table 1.

(Evaluation Method) (1) Appearance Each support and floppy disk were visually observed and observed with an optical microscope (100 times), and the presence or absence of foreign matter on the surface of the support and the adhesive surface and the occurrence of bubbles were examined. . (2) Curl value Each support and the finished floppy disk were punched into a 3.5-type floppy disk shape, and in the state of standing vertically, the disk center was chucked with a ring and rotated at 60 rpm. Then, a laser displacement meter was used to scan a range of a radial position from the inner circumference in a range of 20 mm to 45 mm in the radial direction, and a difference between a position where the distance between the disk and the displacement meter was shortest and a position where the distance was longest was determined as a curl value.

[0092]

Table 1 Sample Appearance Curl (mm) Example 1 (FD1) Good 0.5 Good Example 2 (FD2) Good 0.4 Good Example 3 (FD3) Good 0.4 Good Comparative example 1 (FD4) 1.7 Poor Comparative Example 2 (FD5) Good 3.8 Poor Comparative Example 3 (FD6) Good 2.0 Poor

As described above, it can be seen that the magnetic recording media of the examples manufactured according to the present invention have good appearance and curl. In Comparative Example 1, although laminated on both sides of polyethylene terephthalate by the adhesive layer, curl remained due to the influence of deformation of polyethylene terephthalate. Further, in Comparative Examples 2 and 3 in which one film was used as a support without laminating, the warpage unique to the film remained, and the curl amount was large.

[0094]

According to the magnetic recording medium of the present invention, it is possible to produce a support having a small warpage and a small defect on the surface and the adhesive surface, and the floppy disk produced using this support also has a small curl amount. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view of a floppy disk according to the present invention.

[Explanation of symbols]

1 ... floppy disk, 2 ... thermoplastic resin film,
3: magnetic layer, 4: heat-resistant resin film, 5: undercoat layer,
6 ... underlayer, 7 ... magnetic layer, 8 ... seed layer, 9 ... adhesion layer,
10: protective layer, 11: lubricating layer

Claims (5)

[Claims] 1. A floppy disk comprising a heat-resistant resin film having a magnetic layer formed of a ferromagnetic metal thin film on one surface thereof and a heat-resistant resin film having a protective layer formed thereon, and a thermoplastic resin film having magnetic layers formed on both surfaces thereof. A floppy disk characterized in that the disk is heated and bonded so that the outer side is on the outside. 2. The floppy disk according to claim 1, wherein the heat-resistant resin film is selected from an aromatic polyamide film and an aromatic polyimide film. 3. A method for manufacturing a floppy disk, comprising: forming a heat-resistant resin film on which a magnetic layer made of a ferromagnetic metal thin film and a protective layer are formed; A method for manufacturing a floppy disk, comprising: forming a magnetic layer on both surfaces by heating and bonding a thermoplastic resin film and a heat-resistant resin film. 4. The method for producing a floppy disk according to claim 3, wherein at least one of the bonding surface of the heat-resistant resin film and the surface of the thermoplastic resin film is activated and then heat-bonded. 5. The method for producing a floppy disk according to claim 3, wherein the heat bonding is performed by a flat plate hot press or a heat laminating roll at a temperature higher than the melting point of the thermoplastic resin film.