JP2000057558A - Base film for storage medium and magnetic storage medium using such film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To design a base film for a storage medium such that the film surface is provided with proper projections as well as smoothness and also with superior dimensional stability by structuring the base film with a conjugate material made up of a resin and an interlayer compound. SOLUTION: A base film for a storage medium is constituted of a conjugate material made up of a resin and an interlayer compound; the height of the projections, which are formed on the surface of the conjugate material with the interlayer compound, are unevenly distributed in the range of 20 nm or below in the quantity of 90% or more of the total projections. The interlayer compound, for which swelling silicate is organically processed by organic onium ion, is uniformly diffused in the resin. The sheet-shaped interlayer compound with a thickness of 1 nm to a reversal tens nms is oriented parallelly to the surface of the conjugate material and dispersed, thereby enabling a surface to be formed suitable for the base film for the storage medium. With the resin containing the interlayer compound, a low line expansion coefficient can also be obtained. As the resin, the one facilitating a superior strength for the film is used such as polyester resin and polycarbonate resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base film for a recording medium comprising a composite comprising a resin and an interlayer compound, and a magnetic recording medium using the same.

[0002]

2. Description of the Related Art In recent years, as the capacity of recording media represented by magnetic recording media has rapidly increased, demands for smoothness of base films for recording media have become strict. In a thin-film magnetic recording medium such as a high-capacity magnetic tape, the magnetic layer is thin and fine projections on the surface of the base film tend to appear as projections on the surface of the magnetic layer. Protrusions on the surface of the magnetic layer cause recording / reproducing errors.

[0003] However, if there are no projections on the film surface, the film becomes less slippery, and the runnability of the film or magnetic tape deteriorates. For this reason, it is important that the base film for a recording medium has an appropriate roughness while having a smooth surface.

[0004]

As a method for coping with such a problem, a method of adding a small amount of an inorganic filler to a resin to form fine projections on the surface is disclosed in Japanese Patent Laid-Open No. 60-12 / 1985.
No. 7523 and JP-A-61-246919. However, simply dispersing the spherical inorganic filler causes frequent recording / reproducing errors due to variations in the height of the projections on the surface, that is, it is insufficient as a base film for a recording medium. Was.

[0005] The base film for a recording medium must have fine projections on the film surface, and the projections must be uniform in height. For this reason, Japanese Unexamined Patent Publication No. Hei.
No. 114830 and Japanese Patent Publication No. 6-55491.

However, such a method has problems in manufacturing such as requiring special equipment in a multi-layering process and making it difficult to cope with thinning of a film. Further, since the inorganic filler is unevenly distributed in the film, there is a quality problem that the film is easily peeled off at the portion where the filler is unevenly distributed when the film or the magnetic tape is running.

[0007]

SUMMARY OF THE INVENTION The present invention is a base film for a recording medium comprising a composite comprising a resin and an interlayer compound. According to the present invention, the height of the projections formed on the composite surface by the intercalation compound is 20% or more of the total number of projections.
This is a recording medium base film unevenly distributed in the range of nm or less. The present invention is a magnetic recording medium using a base film for a recording medium composed of a composite composed of a resin and an interlayer compound.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The base film for a recording medium of the present invention comprises a composite comprising a resin and an interlayer compound.
The base film for a recording medium of the present invention is characterized in that an intercalation compound obtained by organically treating a swellable silicate is uniformly dispersed in a resin, and a sheet having a layer thickness of 1 nm to several tens nm. Since the interlaminar compound is dispersed and oriented in parallel with the surface of the composite, a suitable surface can be formed on a base film for a recording medium. Further, by containing an interlayer compound in the resin, the coefficient of linear expansion can be reduced.

The resin used in the present invention is a film having excellent strength such as a polyester resin such as polyethylene terephthalate and polyethylene naphthalate, a polycarbonate resin, an aromatic polyamide resin, an aromatic polyimide and the like. Is a resin easily obtained. In particular, aromatic polyimide resins are preferably used because of their excellent heat resistance. The aromatic polyimide resin is a resin obtained by performing a dehydration reaction of a polyamic acid obtained by a condensation reaction between a tetracarboxylic dianhydride and a diamine.

Examples of the tetracarboxylic dianhydride include pyromellitic acid, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-diphenylethertetracarboxylic acid Acid dianhydride, 3,3 ', 4
4'-diphenyltetracarboxylic dianhydride, 1,4-
Hydroquinone dibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride may be mentioned, and one or more kinds thereof may be used in combination.

In particular, use of 1,4-hydroquinone dibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride to obtain an aromatic polyimide resin having a low water absorption and a high elastic modulus. Is preferred. As the diamine, paraphenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, 2,2-
Bis [(4-aminophenoxy) phenyl] propane is mentioned, and one kind or a mixture of two or more kinds can be used.

In particular, it is preferable to use 4,4'-diaminobenzanilide in order to obtain an aromatic polyimide resin having a high elastic modulus. The intercalation compound used in the present invention,
A compound obtained by allowing an organic onium ion to act on a swellable silicate, in which an organic onium ion is inserted between layers of the swellable silicate.

[0013] Such an intercalation compound is prepared by a known technique (for example, Japanese Patent Publication No. Sho 6 (1988)) in which an organic onium ion is reacted with a layered clay mineral containing a negative layer lattice and exchangeable cations.
1-5492, JP-A-60-42451,
It is manufactured according to Japanese Patent Application Nos. 5-245199 and 5-245200. The above-mentioned swellable silicate mainly comprises a tetrahedral sheet of silicon oxide and an octahedral sheet of metal hydroxide, and examples thereof include smectite group clay and swellable mica.

The above smectite group clay is represented by the following general formula (1): X0.2-0.6 Y2-3 Z4O10 (OH) ₂ .nH ₂ O (1) (where X is K, Na, １ ／ Ca, And 1 / 2Mg
At least one member selected from the group consisting of
e, Mn, Ni, Zn, Li, Al, and at least one member selected from the group consisting of Cr, and Z is at least one member selected from the group consisting of Si and Al. H _{2 O} represents a water molecule bonded to an interlayer ion, and n is remarkably fluctuated according to the interlayer ion and the relative humidity), and is natural or synthetic. Specific examples of the smectite group clay include, for example, montmorillonite, beidellite, nontronite, saponite, iron saponite,
Examples include hectorite, sauconite, stevensite, bentonite, and the like, or substituted substances, derivatives, and mixtures thereof.

The swellable mica is represented by the following general formula (2): X0.5-1.0 Y2-3 (Z4O10) (F, OH) ₂ (2) (where X is Li, Na, K, At least one member selected from the group consisting of Rb, Ca, Ba, and Sr;
g, one or more selected from the group consisting of Fe, Ni, Mn, Al, and Li, and Z is Si, Ge, Al, F
at least one selected from the group consisting of e and B. )
And natural or synthetic. These are substances having the property of swelling in water, a polar solvent compatible with water at an arbitrary ratio, and a mixed solvent of water and the polar solvent. For example, lithium-type teniolite, sodium-type teniolite, lithium-type Examples thereof include silicon mica, sodium tetrasilicic mica, and the like, and substituted substances, derivatives, and mixtures thereof. The following equivalents of vermiculite can also be used.

The vermiculite has three octahedral types and two
There is octahedral, the following general formula (3) (Mg, Fe, Al) 2~3 (Si4-xAlx) O10 (OH) 2 · (M +, M2 + 1/2) x · nH 2O (3) ( where M is an exchangeable cation of an alkali or alkaline earth metal such as Na and Mg, x = 0.6 to 0.9, n =
3.5-5).

The swellable silicates described above are used alone or in combination of two or more. The crystal structure of the swellable silicate is desirably high in purity, which is regularly stacked in the c-axis direction, but a so-called mixed layer mineral in which the crystal cycle is disordered and a plurality of types of crystal structures are mixed may be used.
The organic onium ion has a structure represented by an ammonium ion, a phosphonium ion, a sulfonium ion, and an onium ion derived from a heteroaromatic ring. The presence of the onium ion can introduce an organic structure having a small intermolecular force between the layers of the negatively charged swellable silicate, thereby increasing the affinity between the swellable silicate and the resin.

Examples of the organic onium ions include alkylamine ions such as laurylamine ion and myristylamine ion, ammonium ions such as diethylmethyl (polypropylene oxide) ammonium ion and dimethylbis (polyethylene glycol) ammonium ion, and glycol. Examples include an ammonium ion having a chain.

The structure of the intercalation compound dispersed in the base film for a recording medium of the present invention has an agglomeration structure of μm size in which a plurality of layers of the swellable silicate before the organic treatment are laminated. Completely different. That is, an organic onium ion having an affinity for the resin is introduced between the layers, and the interlayer compound is dispersed in the resin in a very fine and independent flake shape by using an interlayer compound in which the interlayer is expanded. . Such a dispersed state of the flaky interlayer compound can be expressed by the following parameters.

First, when the average layer thickness is defined as the number average value of the layer thickness of the silane clay composite dispersed in a flaky shape,
The upper limit of the average layer thickness of the interlayer compound in the base film for a recording medium of the present invention is preferably 150 ° or less.
More preferably, it is 100 ° or less. Although the lower limit of the average layer thickness of the silane clay composite is not particularly limited,
It is about. If the average layer thickness of the silane clay composite is not in the above range, it is difficult to form a smooth surface having an appropriate roughness.

When the maximum layer thickness is defined as the maximum value of the layer thickness of the interlaminar compound dispersed in a flake form in the base film for a recording medium, the maximum thickness in the base film for a recording medium of the present invention is defined as follows. The upper limit of the maximum thickness of the interlayer compound is preferably 1500 °. More preferably, it is 1200 °, and still more preferably 1000 °. The upper limit of the maximum layer thickness is 1500
If it is larger than Å, it is difficult to form a surface having an appropriate roughness while being smooth. The lower limit of the maximum thickness of the interlayer compound is not particularly limited.

The above-mentioned layer thickness can be determined from an image taken using a microscope or the like. That is, suppose that X-
A thin film is cut out from the recording medium film placed on the Y surface in a plane parallel to the XZ plane or the YZ plane, and the thin section is subjected to a high magnification of about 4 to 100,000 times or more using a transmission electron microscope or the like. Can be determined by observation. The measurement is performed by placing an arbitrary region containing 100 or more intercalation compounds on an elephant of a transmission electron microscope obtained by the above method, forming an image with an image processing device or the like, and performing computer processing. Can be quantified. Alternatively, it can also be obtained by measuring using a ruler or the like.

The intercalation compound in the base film for a recording medium of the present invention is such that a flaky (sheet-like) intercalation compound is oriented parallel to the surface of the composite and dispersed. Therefore, the projections formed on the film surface by the intercalation compound are unevenly distributed in a limited height, and can form a surface having an appropriate smoothness, which is important as a base film for a recording medium. .

The center line average roughness (Ra) of the surface of the film having the protrusions formed by the interlayer compound is 0.5 to 0.5.
A range of 10 nm is preferable, and 1 to 5 nm is more preferable. If it is less than 0.5 nm, the film will be too smooth, impairing film running properties. Conversely, if it is larger than 10 nm, recording / reproducing errors in a recording medium will occur.

In order to set the center line average roughness (Ra) of the surface within the above range, a method of adjusting the type of the interlayer compound, the concentration in the resin, and the like can be mentioned. As an effect other than that described above in which the interlayer compound is contained, characteristics such as an elastic modulus and a linear expansion coefficient of the resin can be improved. By improving the characteristics with an interlayer compound, it is possible to produce a thinner base film for a recording medium.

For example, even if the inherent elastic modulus of the resin is insufficient for thinning the film, the elastic modulus can be improved by including an interlayer compound. Although the elastic modulus of the composite is not particularly limited, it is 800 kgf / mm.
^Two or more are preferred. . If the elastic modulus is less than 800 kgf / mm ² , if the thickness is reduced to 10 μm or less, there is no sufficient strength as a carrier. The coefficient of linear expansion of the composite is 50 ° C.
10 ppm or less is preferable in the range of 150 ° C. 10pp
If it is more than m, curl will be generated after forming a metal layer such as a magnetic layer at a high temperature.

The base film for a recording medium of the present invention can be suitably used for a high-density magnetic recording medium. The kind of metal or metal compound used as a magnetic material is a magnetic layer such as iron, cobalt, nickel There is no particular limitation as long as a known ferromagnetic layer having chromium, chromium, or an oxide or alloy thereof can be formed. In addition, regarding the method of forming the magnetic thin film, plating, vacuum evaporation, sputtering,
A wet coating method in which a ferromagnetic powder or a vacuum thin film forming technique such as an ion plating method is applied as a magnetic paint using a binder composed of, for example, vinyl chloride, vinyl acetate, vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate. Method can be used. At this time, the binder
Is preferably a thermosetting or radiation-curing binder, and may further contain a dispersant, a lubricant, an antistatic agent and the like as other additives.

The method for producing the base film for a recording medium of the present invention will be specifically described with reference to an aromatic polyimide film as an example from the group of resins which can best achieve the object of the present invention. It is not limited. Formula (1) which is an aromatic polyimide precursor

[0029]

Embedded image

(Wherein R1 represents a tetravalent organic group and R2 represents a divalent organic group). A mixed solution of a polyamic acid represented by the formula (I) and an intercalation compound (hereinafter, a clay dispersion) is prepared. The polyamic acid can be produced by a known method. That is, it is obtained by polymerizing tetracarboxylic dianhydrides and aromatic diamines in an organic polar solvent using substantially equimolar amounts.

Examples of the organic solvent used for the polyamic acid formation reaction include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, and N, N -Dimethylacetamide, N, N-
Acetamide solvents such as diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenols such as phenol, o-, m-, or p-cresol System solvents and the like can be mentioned, and it is desirable to use these alone or as a mixture, but it is also possible to use aromatic hydrocarbons such as xylene and toluene. Further, the polyamic acid is contained in the organic polar solvent in an amount of 1 to 40% by weight, preferably 5 to 40% by weight.
25% by weight is desirable from the viewpoint of handling.

In the polymerization of the polyamic acid, the weight average molecular weight of the polyamic acid is not particularly limited, but is preferably 150,000 or more, more preferably 200,000 or more. If the weight average molecular weight is 150,000 or less, an aromatic polyimide film having poor strength can be obtained. The method of mixing with the polyamic acid solution or the intercalation compound is not particularly limited, and either a method of adding the intercalation compound to the polyamic acid solution in a solid state or a method of adding the intercalation compound in a state of a dispersion previously dispersed in a dispersion medium is used. Although a method may be used, it is important that the mixture is stirred under mechanical shearing by a kneader or the like until the mixture becomes uniform after the addition.

For efficient mixing, it is desirable to apply a shearing speed of 500 rpm or more, or 300 (1 / s) or more, for the rotation speed of the stirrer. The upper limit of the number of revolutions is 25,000 rpm, and the upper limit of the shear rate is 500.
000 (1 / s). Even if the stirring is performed at a value larger than the upper limit, the effect does not tend to change anymore,
It is not necessary to stir at a value greater than the upper limit.

In the intercalation compound contained in the clay dispersion obtained by the above method, the initial layered / agglomerated structure such as the swellable silicate has almost completely disappeared, and the interval between the layers is increased. As a result, a so-called swollen state is obtained. The interlayer compound can be added at any stage. For example, a method of adding a polyamic acid to a polymerizable monomer solution before polymerization, or a method of adding the polyamic acid during the polymerization, or a method of adding the polyamic acid after thermal or chemical imidization, that is, an imide resin A method of adding to a solution or the like can be used.

In order to obtain an aromatic polyimide film from the clay dispersion, any of (1) a thermal method of thermally dehydrating and imidizing and (2) a chemical method using a dehydrating agent may be used. However, it is more preferable to use a chemical method that makes it easy to obtain an aromatic polyimide film having excellent mechanical properties such as elongation and strength. An example of a method for producing an aromatic polyimide-based film from a clay dispersion will be described. (1) The above mixed solution is cast or coated on a drum or an endless belt to form a film, and the film is formed into a film until it has a self-supporting property.
Dry at a temperature below 0 ° C. for about 5-60 minutes. Then
After peeling this off from the support and fixing the end, drying and imidation are performed by gradually heating to about 100 ° C. to 500 ° C. while limiting the shrinkage of the film, and after cooling, it is removed from the aromatic polyimide-based film. Get.

In the above-mentioned production method, a mixed solution obtained by further adding a release agent to the mixed solution in place of the mixed solution of the polyamic acid and the intercalation compound may be used in order to easily peel the self-supporting film from the support. . Examples of the release agent include aliphatic ethers such as diethylene glycol dimethyl ether and triethylene glycol dimethyl ether.
Tertiary amines such as ters, pyridine and picoline; and organic phosphorus compounds such as triphenylphosphine and triphenylphosphate.

When an aromatic polyimide film is obtained by a chemical method, a mixed solution of a polyamic acid and an intercalation compound is replaced with a dehydrating agent having a stoichiometric amount or more and a tertiary amine having a catalytic amount. The added mixed solution may be used. Examples of the dehydrating agent include aliphatic or aromatic acid anhydrides such as acetic anhydride and phthalic anhydride. Examples of the catalyst include aliphatic tertiary amines such as triethylamine, and heterocyclic tertiary amines such as pyridine, picoline and isoquinoline.

In forming a film from the clay dispersion, a film having self-supporting properties after being separated from the support may be stretched. This is because a film having excellent mechanical properties can be easily obtained by stretching. For the purpose of improving various properties such as adhesiveness and heat resistance to a base film for a recording medium, titanium oxide, calcium carbonate, alumina and silica gel are contained in the composite to such an extent that surface properties such as smoothness are not impaired. Including fine particles other than the intercalation compound such as, a film surface is coated with a surface modifier such as a silane coupling agent or a solution containing fine particles and a binder resin, or a discharge treatment such as a corona treatment or a plasma treatment. And so on.

In the base film for a recording medium of the present invention, a specially shaped projection is formed on the film surface because the interlayer compound is dispersed in the film in a direction parallel to the film surface. Moreover, it has a high elastic modulus, a low coefficient of linear expansion, and is excellent in transparency and toughness, so that it can be used as a base film for recording media such as high-density magnetic recording media.

[0040]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. First, evaluation methods in Examples and Comparative Examples are summarized below. 1. Protrusion Height The fine projection height was measured using an electron beam three-dimensional roughness analyzer (ERA-8000, manufactured by Elionix) at a cutoff value of 0.008 mm and a measurement length of 110 μm.

From the obtained measurement results, the number of peaks with respect to a predetermined peak height was analyzed at intervals of 5 nm to calculate the height of the protrusions and the number thereof. Height is 20 nm as projection height ratio
The following ratio of the number of projections to the total number of projections was calculated by the following equation. Protrusion height ratio (%) = number of protrusions of 20 nm or less / total number of protrusions × 100 Similarly, calculation was performed for protrusions of 15 nm or less. 2. Center line average roughness Center line average roughness Ra (nm) was measured using a three-dimensional surface structure analysis microscope (manufactured by ZYGO, NewView 200).
Measured with a cutoff value of 0.008 mm and a measurement length of 1 mm,
The average value of 10 measurements was shown. Note that Ra is defined by JI
This is shown in SB0601. 3. Drivability Using a VHS video tape recorder, a magnetic tape
Screen fluctuations due to disturbances in running were observed. The atmosphere was at room temperature and humidity of 25 ° C. and 55% RH. The case where there was no fluctuation of the screen was indicated by “○”, and the case where the running was sometimes delayed and the screen flickered was indicated by “×”. 4. Linear expansion coefficient Measured in tensile mode using TMA-50 manufactured by Shimadzu Corporation. In addition, the measurement conforms to JISK7197 and is 50 to 15
The value at 0 ° C. was calculated. 5. Dropout Dropout is a 10-minute dropout counter in which a three-stage wave signal is recorded on a magnetic tape with an optimum recording current, and the dropout of the video head amplifier output during reproduction is 18 dB and the duration is 20 μsec or more. The measurement was performed in-and the average was shown per minute. Next, an example of preparation of a polyamic acid solution and an interlayer compound dispersion will be described.

ODA is 4,4'-diaminodiphenyl ether, DABA is 4,4'diaminobenzanilide, BPDA is 3,3 ', 4,4'-diphenyltetracarboxylic dianhydride, TMHQ is , 1,4-hydroquinone dibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride and NMP represent N-methyl-2-pyrrolidone. (Preparation of polyamic acid solution A-1) DAB at room temperature
0.095 mol of TMHQ was added to an NMP solution of 0.08 mol of A and 0.02 mol of ODA, and the mixture was stirred for 1 hour in a nitrogen atmosphere. Next, slowly add TMHQ to this solution.
A 0.005 mol NMP solution was added to obtain a 15% by weight polyamic acid solution. (Preparation of polyamic acid solution A-2)
0.095 mol of BPDA was added to an NMP solution of 0.08 mol and 0.02 mol of ODA, and the mixture was stirred for 1 hour in a nitrogen atmosphere. Then, slowly add BPDA 0.
A 005 mol NMP solution was added to obtain a 15% by weight polyamic acid solution. (Preparation of Intercalation Compound Dispersion B-1) Intercalation Compound MTE
(Manufactured by Corp Chemical Co., Ltd. and treated with swellable mica with methyltrioctylammonium ion)
After stirring and dispersing at 0 ° C. for 3 hours, the mixture was further treated with ultrasonic waves for 5 minutes to obtain a liquid in which 5% of an intercalation compound was dispersed in NMP. (Preparation of Intercalation Compound Dispersion B-2) Intercalation Compound MPE
(Cup Chemical Co., Ltd., swellable mica treated with diethyl (polypropylene glycol) ammonium ion) was stirred and dispersed in NMP at 50 ° C. for 3 hours.
Further treat with ultrasonic for 5 minutes, and add 5% of intercalation compound to NMP
A dispersed liquid was obtained.

(Examples 1 to 4) Polyamic acid solution A-
1 to A-3100 parts by weight and interlayer compound dispersion B-1
B-3 was mixed in the combination shown in Table 1 to obtain a clay dispersion. In addition, the compounding number of the interlayer compound to the resin is shown in Table 1. A polyimide-based film was prepared from the obtained clay dispersion. The production of the film is performed as follows. Acetic anhydride 15 g, β-
After adding 5 g of picoline and 10 g of NMP and sufficiently stirring, the mixture was cast on a stainless steel endless belt through a slit die, and then heated at 80 ° C. for 10 minutes to obtain a film having self-supporting properties. After peeling this film from the endless belt, the end is fixed and continuously heated to 100 ° C. to 450 ° C., and further heated at 450 ° C. for 5 minutes for imidization.
A polyimide film containing an interlayer compound having a good transparency and a thickness of 15 μm was obtained. The center line average roughness Ra, the ratio of protrusions, and the coefficient of linear expansion of the obtained polyimide film were measured. The results are shown in Table 1.

The obtained film was loaded into a vacuum chamber,
Glow discharge treatment was performed in an Ar atmosphere of 10 ^-2 torr, and then the vacuum chamber was depressurized to 10 ^-6 torr and the electron beam was deposited while running the film along a drum heated to 150 ° C. To make a Co-Ni alloy (Co 75% by weight, Ni25
Wt%) was deposited to a thickness of 0.5 μm. This was slit to produce a magnetic tape. With respect to the obtained magnetic tape, running performance and dropout characteristics were evaluated. The results are shown in Table 2.

(Example 5) Interlayer compound Polyethylene naphthalate containing 10% by weight of MPE was prepared as a clay dispersion (solid state), and a film was produced by a melt extrusion method. The production of the film is performed as follows. The clay dispersion was melt-extruded by an extruder, cast on a cooling roll through a slit die, and the resin was peeled off the roll to obtain an unstretched film. This unstretched film is stretched 4.0 times in the longitudinal direction at 130 ° C., then stretched 4.2 times in the width direction at 120 ° C., and further stretched in the longitudinal direction at 150 ° C.
Stretched 1.1 times. After stretching the film,
Heating was performed at 0 ° C. for 10 seconds to obtain a polyethylene naphthalate film having a film thickness of 15 μm. The resulting polyethylene naphthalate-based film was measured for center line average roughness Ra, ratio of protrusions, and coefficient of linear expansion, and the results are shown in Table 1.

The obtained film was loaded into a vacuum chamber,
Glow discharge treatment was performed in an Ar atmosphere of 10 ^-2 torr, and then the vacuum chamber was depressurized to 10 ^-6 torr and the electron beam was deposited while running the film along a drum heated to 150 ° C. To make a Co-Ni alloy (Co 75% by weight, Ni25
Wt%) was deposited to a thickness of 0.5 μm. This was slit to produce a magnetic tape. With respect to the obtained magnetic tape, running performance and dropout characteristics were evaluated. The results are shown in Table 2.

Comparative Example 1 A polyimide film was prepared in the same manner as in Examples 1 to 4, except that the polyamic acid solution A-1 was used as it was. About the obtained polyimide film,
The center line average roughness Ra, the ratio of protrusions, and the coefficient of linear expansion were evaluated. Table 1 shows the results. The resulting film was loaded in a vacuum chamber and subjected to glow discharge treatment in an Ar atmosphere of 10 ^-2 torr. Then, the vacuum chamber was depressurized to 10 ^-6 torr and the film was heated to 150 ° C. While traveling along the drum, a Co-Ni alloy (75% by weight of Co, 25% by weight of Ni) was deposited by electron beam evaporation to a thickness of 0.5 μm. This was slit to produce a magnetic tape. With respect to the obtained magnetic tape, running performance and dropout characteristics were evaluated. The results are shown in Table 2.

Comparative Example 2 A polyamic acid solution A-1 and a liquid in which colloidal silica (average particle size: 20 nm) was dispersed in NMP were mixed to prepare a dispersion. The colloidal silica was contained so as to be 5% by weight with respect to the resin.
A polyimide-based film was produced from the obtained dispersion in the same manner as in Examples 1 to 4.

The obtained polyimide film was evaluated for film surface properties (center line average roughness, Ra) and coefficient of linear expansion. Table 1 shows the results. Further, when the shape of the protrusions on the surface was observed, hemispherical protrusions of non-uniform size were unevenly present. The resulting film was loaded in a vacuum chamber and subjected to glow discharge treatment in an Ar atmosphere of 10 ^-2 torr. Then, the vacuum chamber was depressurized to 10 ^-6 torr and the film was heated to 150 ° C. While traveling along the drum, a Co-Ni alloy (75% by weight of Co, 25% by weight of Ni) was deposited by electron beam evaporation to a thickness of 0.5 μm. This was slit to produce a magnetic tape. With respect to the obtained magnetic tape, running performance and dropout characteristics were evaluated. The results are shown in Table 2.

[0050]

As described above, the recording medium base of the present invention is described.
The film has an appropriate projection while the film surface is smooth because the interlayer compound is contained in the resin. Furthermore, it has excellent dimensional stability with a linear expansion coefficient of 10 ppm or less.

[0051]

【table 1】

[0052]

[Table 2]

Claims (8)

[Claims] 1. A base film for a recording medium, which is a composite comprising an interlayer compound obtained by subjecting a resin and a swellable silicate to an organic onium ion. 2. The recording according to claim 1, wherein the composite has fine protrusions formed of an interlayer compound on the surface thereof, and the fine protrusions having a height of 20 nm or less are 90% or more of the total number of the fine protrusions. Base film for media. 3. The base film for a recording medium according to claim 1, wherein the fine projections having a height of 15 nm or less are 80% or more of the total number of the fine projections. 4. A center line average roughness Ra is 0.5 to 10 nm.
4. The base film for a recording medium according to claim 1, wherein: 5. The base film for a recording medium according to claim 1, wherein the center line average roughness Ra is 1 to 5 nm. 6. The base film for a recording medium according to claim 1, wherein the resin is an aromatic polyimide resin. 7. The composite comprising an interlayer compound obtained by subjecting a polyimide resin and a swellable silicate to an organic treatment with an organic onium ion has a linear expansion coefficient of 10 ppm or less. 7. The base film for a recording medium according to item 6. 8. A magnetic recording medium in which a magnetic layer is formed on at least one surface of a composite, using the film according to claim 1.