JP2001283426A - Floppy (r) disk and its manufacture method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supporting body for floppy disk having high dimensional stability and heat resistance and to provide a floppy disk. SOLUTION: The floppy disk has at least a magnetic film, a protective film and a lubricating film laminated on the surface of the supporting body for floppy disk manufactured by press-contacting heat resistant resin films on the both sides of a thermoplastic resin film, then heat-molding the thermoplastic resin film at a state that it is heated up to its melting point or more and stripping the heat resistant resin films after it is cooled to flatten the surface of the supporting body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Magnetic recording media, such as magnetic tapes and hard disks, include a ferromagnetic metal thin film formed on a support by a vacuum film forming method such as a sputtering method or a vapor deposition method. 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 magnetic recording medium such as a hard disk which requires a high recording density.

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 computers due to the spread of notebook computers. However, the temperature inside the notebook computers is high, and the notebook computers are out of the office. It is often used in a wide range of temperatures. 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.
Not commercially available.

For example, polyethylene terephthalate or polyethylene naphthalate, which is widely used as a support for magnetic tapes and floppy disks, has a glass transition temperature much lower than a heating temperature when a magnetic layer is formed by a sputtering method. For this reason, deformation occurs when the magnetic layer is formed, and cracks often occur in the magnetic layer.
Further, when heated to such a temperature, the surface properties of the oligomer are degraded by precipitation on the surface, and the mechanical properties are significantly degraded by hydrolysis.

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. Fluororesin films such as polyetheretherketone, polyetherimide, polyethersulfone, polysulfone, ETFE, PFA, and FEP are thermoplastic, so that it is possible to reduce the warpage, but this is suitable for the purpose of the present invention. Nothing has a smooth surface.

Whatever material is used for the support, if the surface is smoothed to a certain degree or more, handling such as transport and winding of 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.

In view of the above, there has been proposed a method of forming a support for each sheet by injection molding using a thermoplastic resin such as polyetherimide instead of a roll-shaped film. In order to obtain it, it is necessary to pour the resin into a smooth mold under high temperature. In such a case,
Since the resin and the mold adhere to each other and the resin cannot be removed from the mold, it cannot be used.

[0011]

SUMMARY OF THE INVENTION The present invention provides a floppy disk support having smooth surface properties, high heat resistance, low warpage, and high dimensional stability, and a floppy disk medium suitable for high-density recording. It is something to offer.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a floppy disk having at least a magnetic film on a smooth thermoplastic film surface produced by pressing a heat-resistant resin film on both surfaces of a thermoplastic resin film and thermoforming. This is a floppy disk on which a protective film and a lubricating film are laminated. The above-mentioned floppy disk wherein the thermoplastic resin film is selected from the group consisting of polyetherimide, polyetheretherketone and polyethersulfone. This is the above-mentioned floppy disk in which an undercoat film is provided on both surfaces of a thermoplastic resin film.

The present invention also relates to a method of manufacturing a support for a floppy disk, wherein a thermoplastic resin film for a support is heated to a melting point or higher, and a heat-resistant resin film is pressed on both surfaces thereof. This is a method for producing a support for a floppy disk, in which a resin film is thermoformed in a state of being heated to a temperature not lower than its melting point, and after cooling, the heat resistant film is peeled off to smooth the surface.

In the method of manufacturing a support for a floppy disk, a heat-resistant resin film is pressed and molded on both sides of a thermoplastic resin film for the support, and after cooling, the heat-resistant film is peeled off to smooth the surface. This is a method for producing a support for a floppy disk. The method for producing a support for a floppy disk as described above, wherein the thermoplastic resin film is at least one selected from the group consisting of polyetherimide, polyetheretherketone, and polyethersulfone. The method for producing a support for a floppy disk as described above, wherein the heat-resistant resin film is one of an aromatic polyimide and an aromatic polyamide.
The method for producing a support for a floppy disk, wherein the smoothing film is provided on the surface of the heat-resistant resin film.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a thermoplastic resin film is heated to a temperature not lower than its melting point, heat-resistant resin films are pressed and molded on both surfaces of the thermoplastic resin film, and after cooling, the heat-resistant resin film is drawn. This is one in which a layer such as a magnetic film is formed on a smooth surface formed by peeling. FIG. 1 is a diagram for explaining a floppy disk of the present invention, and is a cross-sectional view. In the floppy disk 1 of the present invention, a lower coating 3 is laminated on both surfaces of a thermoplastic resin film 2, and a magnetic film 4 is formed on the lower coating 3 directly or via a base film. . Further, a protective film 5 is formed on the magnetic film 4, and a lubricating film 6 is formed on the protective film 5.

As the thermoplastic resin film used in the present invention, generally used thermoplastic resins can be used. However, considering heat resistance, polyimide, polyetheretherketone, polyethersulfone, polyetherimide, polysulfone , Polyphenylene sulfide, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), alkyl vinyl ether copolymer (PF
A), tetrafluoroethylene-ethylene copolymer (E
Fluororesins such as TFE) are preferred. Further, in consideration of the mechanical properties of the support, polyetheretherketone, polyetherimide, and polyethersulfone are particularly preferred.

The heat resistance of the heat-resistant resin is determined in consideration of the temperature reached by the support in the manufacturing process such as the thermosetting temperature when a magnetic film is sputtered or an undercoat film is applied. For example, when the support is heated to about 200 ° C. by the heating of the substrate and the heat of the plasma during sputtering, it is necessary to use a thermoplastic film having high heat resistance such as the above polyetheretherketone, and conversely, When sputtering is performed while cooling the film, the temperature rise of the film is limited only to the very surface exposed to the plasma, so that polysulfone may be sufficient in some cases.

It is preferable that the glass transition temperature or the secondary transition temperature of the thermoplastic resin is higher than the substrate heating temperature during sputtering. The same applies to the case where the substrate is heated in the step of curing the undercoat film or forming the protective film other than the magnetic film sputtering. The glass transition temperature or the secondary transition temperature of the thermoplastic resin is determined by the substrate heating temperature in these steps. Preferably, it is higher than the temperature.

Since this thermoplastic resin film is used after being melt-compressed as described later, a film having a general surface roughness can be used, but a film having a smooth surface roughness is preferable.
Specifically, the surface roughness measured by an optical surface roughness meter is within 10 nm, preferably 5 nm or less, as a center line average roughness Ra, and the projection height measured by a stylus roughness meter is 1 μm or less, preferably Is within 0.1 μm. This surface roughness is preferably substantially the same on the front and back surfaces. In addition, since foreign matter and the like becomes a surface defect, it is necessary to prevent the foreign matter.
The thickness of this thermoplastic film is 3 to 150 μm, preferably 25 to 100 μm.

Specific examples of the polyetheretherketone film and the polyethersulfone film include Sumilite film manufactured by Sumitomo Belite Co., Ltd., and specific examples of the polyetherimide film include Superior Film manufactured by Mitsubishi Plastics, Inc. Is raised.

The heat-resistant resin film used in the present invention comprises:
Aromatic polyimide films and aromatic polyamide films are preferred. This is because these films are stable even at the temperature at which the thermoplastic resin film melts, and are inert to the thermoplastic resin film. Therefore, the thermoplastic resin film and the heat-resistant resin film can be easily peeled off without impairing the surface properties even if they are pressure-bonded by the method described below.

In the present invention, if the thermoplastic resin film is to be molded directly from a mirror-polished metal, glass, silicon substrate, or the like without using these heat-resistant resin films, the thermoplastic resin film resin becomes Strongly adhered, making it impossible to peel off.

It is preferable that the surface in contact with the thermoplastic resin when the heat resistant film is pressed is as smooth as possible. In the present invention, the surface property of the thermoplastic resin film as the support is determined by the surface property of the heat-resistant resin film, and the surface property of the floppy disk to be produced has a very strong influence on its electromagnetic conversion characteristics. To give. Specifically, the surface roughness measured by an optical surface roughness meter is within 5 nm of the average center line roughness, and the projection height measured by a stylus roughness meter is within 0.1 μm. More preferably, the surface roughness measured by an optical surface roughness meter is 1 nm or less in average center line roughness, and 0.06 μm or less in projection height measured by a stylus roughness meter. When the heat-resistant resin film has a rough surface and cannot be used, it is necessary to provide a smoothing film on the surface of the heat-resistant resin film. As the smoothing film, a polyimide resin or a silicone resin is preferable. This smoothing film can be formed by the same method as the undercoating on the thermoplastic resin film described later.

In the present invention, the surface properties of the heat-resistant resin are transferred to the thermoplastic resin film. Generally, the surface defects of the film are often in the form of protrusions, and such protrusions are transferred to the thermoplastic resin film. When it is done, it becomes concave. In the case of a floppy disk, a high projection which becomes a surface defect is likely to cause a scratch by colliding with the head, which is very problematic. However, although a dent causes an error in a recording signal, it does not cause a practical problem due to error correction. This is one of the great effects of the present invention.

The heat-resistant film may contain a filler, but preferably does not contain a filler in order to smooth the surface properties after molding.
The thickness of this heat-resistant film is preferably in the range of 2 to 100 μm, particularly preferably 3 to 25 μm.

Specific examples of the aromatic polyimide film include Upilex (Ube Industries, Ltd.), Apical (Kanebuchi Chemical Co., Ltd.), and Kapton (Toray Dupont). Specific examples of the aromatic polyamide film include Aramica manufactured by Asahi Kasei Kogyo Co., Ltd., and Miktron manufactured by Toray Industries, Inc.

In the present invention, a thermoplastic resin film is sandwiched between the above-mentioned two heat-resistant resin films and pressed and molded, but the number of thermoplastic resin films may be one or plural. . In order to prevent warping in a wide environment, the same film may be laminated and bonded back to back, and in order to adjust mechanical properties,
Different materials may be combined to form a composite film.

The thickness of the support of the present invention is 25 to 12
0 μm, preferably 30 to 75 μm. The optimum thickness of the support depends on the material of the film, the size of the floppy disk, and the recording / reproducing method of the floppy disk drive.

The method for molding a thermoplastic resin film in the production method of the present invention includes a heat-resistant resin film, a thermoplastic resin film, and a mirror-finished surface on a metal, glass, or silicon substrate which has been mirror-polished to prevent undulation. Lamination is performed in the order of the polishing substrates, and this is heated and molded. As the heat molding method, a flat plate hot press, thermoforming with a hot roll, high-frequency heating molding and the like can be used, but a flat plate hot press is preferable. The heating temperature at this time is equal to or higher than the melting point of the thermoplastic resin film.

When a flat plate hot press is used, a mirror-polished substrate, a heat-resistant comb film, a thermoplastic resin film, a heat-resistant resin film, and a mirror-polished substrate may be stacked in this order and thermally bonded one by one. However, a plurality of sheets may be laminated and pressed at once, and the whole may be heated and molded by a heating means such as an oven. 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 produced, and a thermoplastic resin film having a high melting point can be molded. is there. At this time, the press is preferably performed in a vacuum in order to prevent the generation of air bubbles on the bonding surface and to prevent dust from adhering to each film. Further, in order to prevent generation of bubbles due to gas generated from the film, it is preferable to perform preliminary heating before heating to the bonding temperature. The preheating temperature is preferably 100 ° C. or higher and equal to or lower than the melting point of the thermoplastic resin.

The surface roughness of the mirror-polished substrate used for the pressing surface is preferably sufficiently smoother than the surface of the heat-resistant resin film used. If the surface is rough, this surface is transferred to the support, and the support surface is exposed. An appropriate pressing pressure is 1 × 10 ⁻² MPa to 10 MPa. Since the heating time depends on the thermal and chemical properties of the thermoplastic resin film, it is appropriately selected from several seconds to several hours. After the molding and sufficient cooling, the heat-resistant resin film is peeled off, whereby a thermoplastic resin film with sufficiently smooth both sides and less warpage can be obtained.

When a thermoforming method using a heat roll is used, a heat-resistant resin film, a thermoplastic resin film, and a heat-resistant resin film may be stacked in this order and molded one by one in a batch manner. It may be molded continuously to a roll. In the case of molding by a batch method, a film is superimposed on a smooth heating plate, and is molded by pressing the film with a hot roll or by passing the laminated film between hot rolls. In the case of continuous molding, a film is formed between hot rolls. The heating time at this time depends on the thermal and chemical properties of the thermoplastic resin film, but is within several seconds in principle. For this reason, the surface temperature of the heat roll often needs to be set higher than the melting point of the thermoplastic resin film. As the heat roll, general steam heating or hot oil heating can be used. In the case of a thermoplastic resin film having a high bonding temperature, an induction heating roll is used.

In order to prevent the generation of bubbles due to the gas generated from the film, it is preferable to perform preheating before heating to the bonding temperature. The preheating temperature is preferably 100 ° C. or higher and equal to or lower than the melting point of the thermoplastic resin.
Further, the surface property of the heat laminating roll is preferably smoother than the support used. If the surface is rough, this surface is transferred to the support and the support surface is exposed. 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. Laminate roll pressure is 1kN / m
〜１０10 kN / m is appropriate.

Next, the undercoat film usable in the present invention will be described. When the surface property of the thermoplastic resin film molded in the present invention is insufficient, it is preferable to form an undercoat film for smoothing on the surface of the thermoplastic resin film. Since the undercoat film requires heat resistance more than a thermoplastic resin film, it is necessary to use a polyimide resin, a polyamide imide resin, a silicone resin, a fluorine-based resin, and the like, and cannot use a general polyester resin, a urethane resin, or the like. . 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 film. The thickness of the undercoat film is preferably 0.1 to 3 μm. Further, the undercoat film may be formed before or after bonding the heat-resistant resin film and the thermoplastic resin film.

An example of the use of the thermosetting imide resin is a polyimide resin which is a thermal compound of an imide monomer having two or more terminal unsaturated groups in the molecule. An example of such an imide monomer is pisallylnadiimide 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. The thermosetting polyimide resin preferred in the present invention is a polyimide prepared by first applying an imide monomer onto a heat-resistant resin film and then thermally polymerizing the polyimide, instead of providing the already polymerized polyimide. 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 provided on various non-magnetic supports such as 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 naturally has a lower molecular weight than polyimide, the viscosity of the solution is low. When this solution is applied on a non-magnetic support, the imide monomer has good wraparound to unevenness and a 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 is a divalent linking group such as an aliphatic or aromatic group, and is not particularly limited. 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 solubility of the imide monomer in the solvent and the heat resistance of the polyimide resin as a polymer thereof are mainly determined by the structure of R ³ . Thus the desired characteristics are achieved by selecting the structure of R ^3.

Such a compound was obtained from Maruzen Petrochemical Company in BA
It is commercially available as NI series and ANI series.
The undercoat film of the present invention may contain components other than the imide monomer. For example, a curing agent for promoting 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 film, 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, toluene, xylene,
It is soluble in acetonitrile, cyclohexanone, methyl ethyl ketone, acetone, etc., and in some structures it is also soluble in isopropyl alcohol, ethanol, methanol, etc. These mixed solvents can be used as the solvent.

Further, as a preferred example of the thermosetting silicone resin in the present invention, a silicone resin prepared by a sol-gel method using a silicon compound into which an organic group has been introduced as a raw material can be mentioned. 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 to a heat-resistant resin film and cured, a general-purpose solvent can be used, and the wraparound to unevenness is good.
High smoothing effect. Further, the polycondensation reaction proceeds from a relatively low temperature by the addition of a catalyst such as an acid or a chelating agent, so that 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 has a structure represented by the following chemical formula 2.

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However, R and R 'are monovalent organic groups such as a methyl group A is a divalent organic group such as an alkylene group or none (directly connected)
B is a monovalent group X + such as an alkoxy group, a halogen, and a hydroxyl group.
Y + Z = 4. In Chemical Formula 2, A is preferably absent or a methylene group.

B is preferably an alkoxy group in consideration of reactivity and corrosiveness to the magnetic film, and particularly preferably an alkoxy group having 4 or less carbon atoms such as a methoxy group for facilitating the polymerization reaction. X is preferably 1 or 2, but is 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.

The following are specific examples. ◎

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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, or a halogen. , A monovalent group selected from hydrogen, i + j + k = 4.

In the structure of Formula 1, A is preferably hydrogen. R represents a methyl group, an ethyl group, or the like. It is a monovalent organic residue. X is preferably an alkoxy group in consideration of reactivity and corrosiveness to the magnetic film, and particularly preferably an alkoxy group having 4 or less carbon atoms such as a methoxy group in order to facilitate the polymerization reaction. M is preferably 1 or 2, but particularly preferably 1 in order to facilitate the polymerization reaction.
L is preferably 0 or 1, but particularly preferably 0 for facilitating the polymerization reaction. Therefore, N is particularly preferably 3.

Such compounds include those represented by the following chemical formula. These compounds are described in JP-A-51-111871 and JP-A-63-23224.

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For the purpose of 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 undercoating film 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 hydrocarbon groups, and the smaller the carbon number of R, the more effective the improvement of the heat resistance of the undercoat.

A portion of 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, is hydrolyzed by coating and drying by the method described below.
Polymerizes to form siloxane bonds. 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 as needed.

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, perchlorates and the like are known, but a metal chelate compound is particularly preferred as a curing agent from the viewpoint of lowering the curing temperature and corrosiveness to a magnetic film. 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 undercoating film comprising the above-mentioned thermosetting polyimide resin layer or thermosetting silicone resin layer on a heat-resistant resin film includes a monomer as a raw material and a curing agent if necessary. In addition, a method in which a coating solution dissolved in an organic solvent is applied on a heat-resistant resin film by a method such as a wire bar method, a gravure method, a spray method, a dip coating method, a spin coating method, and then dried can be used. . Further, after that, if necessary, the undercoating film is baked to accelerate the curing, and the heat resistance, the solvent resistance, the adhesion and the like can be improved. 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 baking method for further promoting the curing, heating with hot air, heating with infrared rays, heating with a hot roller, or 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 film afterward, and the film forming temperature, but in the case of about 1 μm, it is in the range of 100 ° C. to 350 ° C., preferably 200 ° C. 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 film, which may hinder the crystal growth of the magnetic film. Conversely, if it is too high, the support may be deformed or productivity may be reduced. In the case of a material that can be polymerized by ultraviolet irradiation, electron beam irradiation, or the like in addition to polymerization by heating, the polymerization reaction may be performed by these irradiations without heating.

Further, by providing very small height projections on the surface of the lower coating film, 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 surface of the magnetic film on the material has a minute projection structure. This micro-projection structure has the effect of significantly improving the handling 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 forming an organic substance projection by applying an emulsion, etc. can be used. preferable. 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 to ensure heat resistance, and such a material is used as an adhesive in the present invention. It is particularly preferable to use a thermosetting imide or a thermosetting silicone resin. The height of the microprojections is 5 to 60 nm, preferably 10 to 30 nm
And the density is 0.1 to 100 / μm ² , preferably 1 to 10 / 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 small. 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. Among them, Ta, Ni-P, Ni-Al,
Cr-Ti is particularly preferred. The thickness of the underlayer is 5 nm to 50 nm, preferably 10 nm to 30 n.
m.

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, Cr, Ti or an alloy thereof, and preferably has a thickness of 15 to 60 nm. Also, these are used in an amorphous state or in a state where the crystallite is smaller than that of the underlayer, unlike the underlayer.

In order to further enhance the adhesion between the undercoat and the seed layer, an adhesion layer may be formed. When the seed layer is not formed, the adhesion between the undercoat and the underlayer is increased. For this purpose, 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 the film while the support is heated, and to use a DC or RF magnetron sputtering method and set the temperature of the support to 100 ° C. to 250 ° C. Is preferred. On the other hand, since the temperature of the support is not only heated but also heated by sputtering, care must be taken.

In the magnetic recording medium of the present invention, it is preferable to provide a protective film on the ferromagnetic metal thin film, and this protective film can significantly improve running durability and corrosion resistance. As the protective film, silica, alumina, titania, zirconia, cobalt oxide, oxides such as nickel oxide,
Examples of the protective film include nitrides such as titanium nitride, silicon nitride, and boron nitride; carbides such as silicon carbide, chromium carbide, and boron carbide; and carbon such as graphite and amorphous carbon. As the protective film, a hard film having a hardness equal to or higher than that of the head material is preferable. Further, a film 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. This film has a Vickers hardness of 10 × 10 ³ MPa or more, preferably 20 × 10 ³ MPa or more. When measured by Raman spectroscopy of a diamond-like carbon film, the film has a hardness of 15 × 10 ³ MPa or more.
A main peak called a so-called G peak is detected around 40 ^-1 cm, and a shoulder called a so-called D peak is detected at 1390 cm ^-1 . These diamond-like carbon films can be prepared by a sputtering method or a CVD method. However, the CVD method is used because the productivity, the stability of quality, and the good abrasion resistance can be ensured even with an ultrathin film having a thickness of 10 nm or less. It is preferable to produce a magnetic species by decomposing carbon-containing compounds such as alkane such as methane, ethane, propane and butane, or alkene such as ethylene and propylene, or alkyne such as acetylene. It is preferable to apply a negative bias voltage to the film or an electrode provided in front of the film to accelerate and deposit the film.

Further, nitrogen gas is mixed with the raw material gas, and C,
By using diamond-like carbon composed of H and N, the coefficient of friction with respect to the head can be reduced. When the thickness of the hard carbon protective film is large, the electromagnetic conversion characteristics are deteriorated and the adhesion to the magnetic layer is reduced, and when the film thickness is small, the wear resistance is insufficient.
The thickness is preferably 2 to 30 nm, particularly preferably 5 to 20 nm.
nm.

In the magnetic recording medium of the present invention, in order to improve running durability and corrosion resistance, it is preferable to add a lubricant or a rust inhibitor to the magnetic film or the protective film. 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), and a perfluoroisopropylene oxide polymer (CF (CF ₃ ) CF
₂₀ ) _n or a copolymer thereof. Specifically, a perfluoromethylene-perfluoroethylene copolymer having a hydroxyl group at a molecular weight terminal (FOMBLIN Z-D)
OL) and the like.

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 are used alone or in combination of two or more. As a method of applying these lubricants on a magnetic film or a protective film, a lubricant is dissolved in an organic solvent and applied by a wire bar method, a gravure method, a spin coating method, a dip coating method, or a vacuum evaporation method. What is necessary is just to make it adhere. The amount of the lubricant to be applied is 1 to 30 mg / m ^2.
Preferably, 2 to 20 mg / m ² is particularly preferred.

Examples of the rust preventives usable in the present invention include nitrogen-containing heterocycles such as benzotriazole, benzimidazole, purine and pyrimidine, derivatives having an alkyl side chain introduced into the mother nucleus thereof, benzothiazole, 2-mercapto Benzothiazole, tetrazaindene ring compound,
Nitrogen- and sulfur-containing heterocycles such as thiouracil compounds and derivatives thereof. These may be mixed with a lubricant and applied on the protective film, or may be applied on the protective film before applying the lubricant, and the lubricant may be applied thereon. Preferably 0.1 to 10 mg / m ² as a coating amount of rust preventives, 0.5 to 5 mg / m ² is particularly preferred.

The tetrasignedene cyclization compounds usable for such a purpose include the following.

◎

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.

[0082]

The present invention will be described below with reference to examples. Example 1 In a molding apparatus 10 shown in FIG. 2, a fluororubber (Viton Co., Ltd.) plate 13 was placed on an aluminum base 12 in a vacuum chamber 11.
Placing the plate heater 15 having a thermocouple was placed a diameter of 8 inch silicon substrate 16 was mirror-polished on the plate heater surface, the maximum protrusion roughness R _max of the smooth surface on the is 0.06 .mu.m, A disk-shaped aromatic polyamide film having an average centerline roughness Ra of 0.8 nm, a thickness of 12 μm, and a diameter of 20 cm is spread so that a smooth surface is on the top, and the average centerline roughness Ra of the surface is 0.2 μm on this. A sample in which two disk-shaped polyetherimide films each having a thickness of 25 μm and a diameter of 18 cm are stacked back to back so that the smooth surface faces outward, and the aromatic polyamide film is further stacked thereon such that the smooth surface faces downward. 17 was placed. On the sample 17, a mirror-polished silicon plate 18 is superimposed,
A plate heater 19 equipped with a thermocouple is placed on 8,
The aluminum plate 20 is placed on the top, and the inside of the molding device 10 is evacuated to 0.1 Pa by a decompression device (not shown) connected to the exhaust port 21. In this state, the sample is preheated at 150 ° C. for 1 hour. did.

Next, pressurization is performed at a pressure of 10 kPa by an air cylinder 22 provided at the upper part of the molding apparatus, and the pressurization is performed.
Heat molding was performed at 0 ° C. for 1 hour. After that, take out the sample,
The aromatic polyamide film on both sides was peeled off to obtain a support 1A. Next, a solution of a thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co., Ltd.) dissolved in ethanol was applied to the surface of the support 1A by dip coating, dried at room temperature, and then at 180 ° C. for 3 hours. Heat, thickness 1.0μ
m undercoat was prepared. Further, an ethanol solution of silica particles having a diameter of 25 nm and a thermosetting imide resin is applied thereon, followed by drying at 180 ° C. for 1 hour. The average height of the projections is about 20 nm, and the density of the projections is 3 / μm. ^Two microprojections were formed. This was designated as support 1B.

Next, the support 1A or 1B is cut out, inserted and fixed in a circular holder to which a uniform tension is applied, and set in a sputtering apparatus for forming a magnetic film.
After heating the support to 150 ° C., a 30 nm Cr—Ti underlayer was formed by DC magnetron sputtering, and a 30 nm Co—Cr—Pt magnetic film was formed. The base film and the magnetic film were formed on both sides of the support. Further, this sample was taken out from the sputtering apparatus, and a protective film made of a diamond-like carbon film having a thickness of 15 nm was formed on the magnetic film by a plasma CVD method using ethane as a raw material.

Next, the sample is taken out of the holder,
A solution in which a perfluoropolyether-based lubricant (FOMBLIN Z-DOL manufactured by Ausimont) is dissolved in a fluorinated solvent (FC-77 manufactured by Sumitomo 3M) is applied on the protective film by dip coating, and lubricated to a thickness of 1 nm. A film was prepared. Then, the sample was punched into a 3.5-type magnetic disk to produce a floppy disk. These samples were used as disks 1A and 1B, respectively.
After the curl measurement described later, this disk was incorporated into a Zip drive shell (manufactured by Fuji Photo Film).

Example 2 In the molding apparatus used in Example 1, the diameter was 20c.
An 8-inch diameter silicon substrate, which has been mirror-polished, is placed on an aluminum plate having a maximum surface roughness of about 8 m.
_max is 0.1 μm, average center line roughness Ra is 1.2 nm,
A circular aromatic polyimide film having a thickness of 25 μm and a diameter of 20 cm is spread so that the smooth surface thereof becomes the upper surface, and a disc-shaped polyetherether having an average center line roughness Ra of 10 nm, a thickness of 25 μm and a diameter of 18 cm is formed thereon. The ketone film was stacked back to back so that the smooth surface was on the outside, and the aromatic polyimide film, the silicon substrate, and the aluminum plate were sequentially stacked thereon such that the smooth surface was on the bottom.

One set of these was set, and 10 sets were stacked. The inside of the molding apparatus was evacuated to 0.1 Pa, and the sample was preheated and heated at 150 ° C. for 1 hour in this state. Next, pressure 100k
It was pressed at Pa and heat molded at 320 ° C. for 1 hour. Thereafter, this film was taken out, and the aromatic polyimide film on both sides was peeled off to obtain a support 2A. Support 2A
An undercoat film, a magnetic film, and the like were formed in the same manner as in Example 1 to obtain a support 2B, a disk 2A, and a disk 2B.

Example 3 In the molding apparatus used in Example 1, the maximum roughness R _max of the smooth surface was 0.06 μm, and the average center line roughness Ra was
Is a thermosetting imide resin (BA manufactured by Maruzen Petrochemical Co., Ltd.) on the surface of an aromatic polyamide film having a thickness of 0.6 nm and a thickness of 12 μm.
A solution of NI-NB) in a mixed solvent of cyclohexanone / ethanol (weight ratio 1: 1) was applied by dip coating, dried at room temperature, and then heated at 350 ° C. for 1 hour.
A smoothing layer having a thickness of 1.0 μm was formed. The surface of this smoothing layer had a maximum projection roughness of 0.04 μm and a center line average roughness of 0.6 nm.

Next, this aromatic polyamide film was spread on a mirror-polished aluminum plate as a square of 20 cm square so that the smooth surface became the upper surface, and the center line average roughness Ra of the surface was 20 nm, the thickness was 25 μm, An 18 cm square polyethersulfone film was stacked back to back so that the smooth surface was on the outside, and the aromatic polyamide film was further stacked thereon such that the smooth surface was on the bottom. After making pre-drying at 150 ° C. for 1 hour in the air, the rolls were heated in vacuum at an induction heating roll having a roll temperature of 350 ° C. while applying a linear pressure of 500 N / m.
The mold was run at a speed of 1 m / sec. This was taken out to the atmosphere, and the aromatic polyamide film on both sides was peeled off to obtain a support 3A. Example 1 of support 3A
In the same manner as described above, a lower coating film, a magnetic film, and the like were formed into a support 3B, a disk 3A, and a disk 3B.

Comparative Example 1 In Example 1, a polyetherimide film having a thickness of 50 μm was used as the support 4A, and an undercoating film was provided directly on the polyetherimide or in the same manner as in Example 1, and then a floppy disk was produced. These were used as a disk 4A and a disk 4B.

Comparative Example 2 A polyetherimide film was formed directly on a silicon substrate in Example 1 without using the heat-resistant resin film of the present invention. However, in this case, the silicon substrate and the polyetherimide film could not be peeled off, and a support could not be produced.

The prepared samples were evaluated by the following evaluation methods. (Evaluation method) (1) Appearance The support and the floppy disk of each example were visually observed and observed with an optical microscope (100 times).
The support was examined for surface roughness. (2) Surface Properties The surface roughness Ra of each of the front and back surfaces of the floppy disk sample was measured using an optical roughness meter for an area of 250 μm square. (3) Curl value Each support and the completed floppy disk were punched out into a 3.5-type floppy disk shape, and the disks were rotated up to 60 rpm with the disk center fixed with a ring while standing upright. Then, the laser displacement meter scans the range of the radial position 20 mm to 45 mm from the inner circumference with respect to this constant radial direction, and the difference between the shortest distance and the longest distance of the disk-displacement meter distance is determined as the curl value. . (4) Electromagnetic Conversion Characteristics The prepared floppy disk was rotated at 3000 rpm, and a signal of 12 MHz was recorded and reproduced with an inductive head at a radial position of 32 mm. The signal output at this time was evaluated relative to the output of Example 1B.

Table 1 shows the results of evaluation of the samples produced in each of the examples and comparative examples based on the above evaluation method.

[0094]

Table 1 Sample Appearance Surface roughness (nm) Curl (mm) Output (dB) Surface Back side Example 1 Support 1A Good Good 0.3 Support 1B Good Good 0.4 Disk 1A Good 1.0 1.1 Good 0.5 -3.9 Disc 1B Good 0.8 0.8 Good 0.6 0 Example 2 Support 2A Good Good 0.2 Support 2B Good Good 0.3 Disc 2A Good 1.5 1.8 Good 0.4 -4.5 Disc 2B Good 0.9 1.1 Good 0.5-1.1 Example 3 Support 3A Good Good 0.9 Support 3B Good Good 0.8 Disc 3A Good 1.1 1.3 Good 1.0 +1.2 Disc 3B Good 1.0 1.0 Good 0.9- 0.9 Comparative Example 1 Support 4A Good Bad 2.6 Support 4B Good Bad 1.9 Disk 4A Good 210 220 Bad 3.4 -12.5 Disk 4B Good 80 110 Bad 2.2-8.9

As can be seen from the above examples, the support and the floppy disk of the examples prepared according to the present invention have better adhesiveness and curl amount as compared with the comparative examples, and are obtained by peeling off the heat-resistant resin film. It can be seen that no surface failure has occurred. Further, it can be seen that the surface properties of the examples using the present invention were improved to almost the same level as the heat-resistant resin film used.

[0096]

According to the present invention, it is possible to produce a support having a small warpage, a smooth surface and few defects, and a floppy disk produced using this support can have a small curl amount.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating an example of a molding device for molding a floppy disk support of the present invention.

[Explanation of symbols]

1 ... floppy disk, 2 ... thermoplastic resin film,
3: Undercoat, 4: Magnetic film, 5: Protective film, 6: Lubricating film, 1
0: molding apparatus, 11: vacuum chamber, 12: base, 13: fluoro rubber plate, 14, 20: aluminum plate, 15, 19 ...
Plate heater, 16, 18 silicon substrate, 17 sample, 21 exhaust port, 22 air cylinder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G11B 5/84 G11B 5/84 AZ // B29K 61:00 B29K 61:00 71:00 71:00 77 : 00 77:00 B29L 9:00 B29L 9:00 17:00 17:00 F term (reference) 4F100 AK01A AK01B AK01C AK47B AK49A AK49B AK54A AK55A AK56A AR00D AR00E BA05 BA07 BA10B BA10E EH662 EJ172 J03J03 EJ422 EJ912 GB03 JK16E JL00E JL04 4F208 AA24 AA32.

Claims (8)

[Claims] In a floppy disk, at least a magnetic film, a protective film, and a lubricating film are laminated on a surface of a smooth thermoplastic film produced by pressing a heat-resistant resin film on both surfaces of a thermoplastic resin film and thermoforming. Features floppy disk. 2. The floppy disk according to claim 1, wherein the thermoplastic resin film is selected from the group consisting of polyetherimide, polyetheretherketone, and polyethersulfone. 3. The floppy disk according to claim 1, wherein an undercoat is provided on both surfaces of the thermoplastic resin film. 4. A method for producing a support for a floppy disk, wherein a heat-resistant resin film is pressure-bonded to both sides of a thermoplastic resin film for a support, and the thermoplastic resin film is heated to a temperature equal to or higher than the melting point. A method for producing a support for a floppy disk, wherein the surface is smoothed by peeling off the heat-resistant film after cooling. 5. A method for manufacturing a support for a floppy disk, comprising: heating a thermoplastic resin film for a support to a temperature equal to or higher than a melting point; pressing and molding a heat-resistant resin film on both surfaces thereof; A method for producing a support for a floppy disk, characterized in that the surface is smoothed by peeling. 6. The support for a floppy disk according to claim 4, wherein the thermoplastic resin film is at least one selected from the group consisting of polyetherimide, polyetheretherketone, and polyethersulfone. How to make the body. 7. The method for producing a support for a floppy disk according to claim 4, wherein the heat-resistant resin film is one of aromatic polyimide and aromatic polyamide. 8. The method for producing a support for a floppy disk according to claim 4, wherein a smoothing film is provided on the surface of the heat-resistant resin film.