JPH0825221B2 - Base film for magnetic recording media - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a base film for a magnetic recording medium.

[0002]

2. Description of the Related Art Aromatic polyamide films or aromatic polyimide films have been investigated for various applications by taking advantage of their excellent heat resistance and mechanical properties. In particular, para-oriented aromatic polyamide is superior to other polymers in mechanical properties such as rigidity and strength, so it is very advantageous for thinning film, and is expected to be used in printer ribbons, magnetic tapes, capacitors, etc. ing. Examples of magnetic recording media include JP-A-58-168655 and JP-A-62-112218.

However, as the process speed of the film processing process, for example, the magnetic layer coating / calendering process for magnetic media applications, is increased, the film running property and the abrasion property of the film surface due to contact roll are deteriorated. Recently, the drawback of causing troubles in the process and product performance has become a problem. Further, when it is used as a magnetic recording tape, the running property with the resin guide pin is remarkably poor, which has recently become a problem.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above problems, maintains the excellent heat resistance and mechanical properties inherent in an aromatic polyamide film or an aromatic polyimide film, and has excellent abrasion resistance and a resin guide pin. The object of the present invention is to provide a film having good running property and excellent electromagnetic conversion characteristics.

[0005]

The present invention is a film comprising an aromatic polyamide or an aromatic polyimide, wherein the film is stretched in at least one direction at a tensile rate of 1000% / min by 1%. Has a film strength of 6 kg / mm ² or more and a cutoff value of 0.08.
The centerline average roughness [Ra] _{0.08 of} at least one surface measured in mm is in the range of 0.001 to 0.01 μm, and the centerline average roughness [Ra] _0.008 measured at a cutoff value of 0.008 mm. [Ra] _0.08 is a base film for a magnetic recording medium, which has the following relationship.

0.5 ≦ [Ra] _0.008 / [Ra] _0.08 ≦ 0.9 ...
The aromatic polyamide of the present invention is preferably one containing 50 mol% or more of the repeating unit represented by the following general formula,
It is more preferably 70 mol% or more. General formula

[0007]

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And / or

[0009]

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Here, Ar ₁ , Ar ₂ and Ar ₃ are, for example,

[0011]

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[0012] is like, X, Y is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S-,
-C (CH _{3) 2} - is selected from. Further, some of the hydrogen atoms on these aromatic rings are halogen groups (especially chlorine), nitro groups, C ₁ -C ₃ alkyl groups (especially methyl groups), C ₁
It also includes those substituted with a substituent such as a C ₃ -alkoxy group, and those in which hydrogen in the amide bond constituting the polymer is substituted with another substituent.

From the viewpoint of characteristics, the above-mentioned aromatic ring bonded in the para-position is 50% or more of the total aromatic ring, preferably 75%.
%, A polymer having a high rigidity and a good heat resistance is preferable. Further, from the viewpoint of reducing the moisture absorption, a polymer in which a part of hydrogen atoms on the aromatic ring is substituted with a halogen group (particularly chlorine) and the aromatic ring is 30% or more of the whole is preferable.

The aromatic polyimide in the present invention is one having at least one aromatic ring and at least one imide ring in the repeating unit of the polymer and has the general formula:

[0015]

[Chemical 4]

Or

[0017]

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It is preferable that the repeating unit represented by is contained in an amount of 50 mol% or more, more preferably 70 mol% or more. Here, Ar ₄ and Ar ₆ include at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar
₄ is derived from aromatic tetracarboxylic acid or its anhydride. The following are typical examples.

[0019]

[Chemical 6]

[0020] wherein Z is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S-,
-C (CH _{3) 2} - is selected from.

Ar ₆ is derived from carboxylic acid anhydride or its halide. Ar ₅ and Ar ₇ are, for example,

[0022]

[Chemical 7]

[0023] is like, X, Y is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S-,
-C (CH _{3) 2} - is selected from. Further, some of the hydrogen atoms on these aromatic rings are halogen groups (especially chlorine), nitro groups, C ₁ -C ₃ alkyl groups (especially methyl groups), C ₁
It also includes those substituted with a substituent such as a C ₃ -alkoxy group, and those in which hydrogen in the amide bond constituting the polymer is substituted with another substituent.

The aromatic polyamide and aromatic polyimide of the present invention may be blended with a lubricant, an antioxidant and other additives, and a polymer, to the extent that the physical properties of the film are not impaired.

The film of the present invention must have a film strength [F-1] ₁₀₀₀ of 6 kg / mm ² or more when the film is stretched by 1% at a tensile rate of 1000% / min in at least one direction. It is more preferably at least 8 kg / mm ^{2, and even} more preferably at least 10 kg / mm ² . Further, it is preferable that the relationship between the film strength [F-1] ₁₀ and [F-1] ₁₀₀₀ when the film is stretched by 1% at a pulling rate of 10% / min satisfies the following expression.

0.7 ≦ [F-1] ₁₀ / [F-1] ₁₀₀₀ ≦ 1 ... [F-1] ₁₀ / [F-1] When the _ratio is less than 0.7, the magnetic tape is In such a case, the strength changes due to the stress variation, which causes a problem that the running property becomes unstable. It is more preferably 0.8 or more.

Further, the cutoff value of the film of the present invention is 0.0
The center line average roughness [Ra] _{0.08 of} at least one surface measured at 8 mm needs to be in the range of 0.001 to 0.01 μm. When the center line average roughness is less than 0.001 μm, the film surface is too smooth and the running property is insufficient,
When it is larger than the above range, the abrasion resistance of the film surface is deteriorated, which often causes a problem in film processing. More preferably, it is 0.003 to 0.01 μm. The center line average roughness [Ra] measured at a cutoff value of 0.008 mm
It is necessary that _0.008 and [Ra] _0.08 have the following relationship.

0.5 ≦ [Ra] _0.008 / [Ra] _0.08 ≦ 0.9 ...
When [Ra] _0.008 / [Ra] _0.08 exceeds 0.9, the waviness of the film surface is small and the running property when used as a magnetic recording tape is poor. When it is less than 0.5, the waviness of the film surface is large and the magnetic recording is large. When the tape is used, the electromagnetic conversion characteristics are significantly deteriorated. The range is more preferably 0.65 to 0.85.

In order for the surface of the film of the present invention to have an appropriate roughness, it is necessary that particles are present in the film. The types of particles include SiO ₂ , TiO ₂ , and Al ₂
Inorganic particles such as O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ , carbon black, zeolite, and other fine metal powders, silicon particles, polyimide particles, crosslinked copolymer particles, crosslinked polyester particles, Teflon particles, etc. Although there are organic polymers and the like, inorganic particles are more preferable from the viewpoint of heat resistance.

Further, the average primary particle diameter of the particles contained in the film of the present invention is 0.005 to 5 μm, preferably 0.0
When the thickness is in the range of 2 to 2 μm, both abrasion resistance and running property are good, which is desirable.

The content of the particles contained in the film of the present invention is 0.01 to 5 wt%, preferably 0.05 to 2 wt.
%. If the content of the particles is less than the above range, the running property of the film will be poor, and conversely if the content is large, the abrasion resistance will be poor, which is not preferable.

The film of the present invention may be a single layer film, but may be a laminated film . The outermost layer of the film and the base layer portion laminated with here (outermost stacked
The film constituent parts other than the film of the layer ) may be the same or different. Particles may be contained in at least one layer constituting the base layer portion, and it is desirable to use the kind of particles, the average primary particle diameter of particles, and the content which are desirably used in the film of the present invention. It is preferable that the diameter of the particles in the base layer portion is larger than the diameter of the particles in the laminated outermost layer film, because the surface of the film can have an appropriate undulation and the tape running property can be further improved.

The thickness of the film of the present invention is 0.5 to 50 μm.
m, more preferably 1 to 20 μm, further preferably 2 to
It is 10 μm.

The film of the present invention has a tensile elastic modulus in at least one direction of 600 kg / mm ² or more, more preferably 800 kg / mm ² or more. Further, the tensile elastic modulus ratio in the longitudinal direction and the transverse direction is 0.3 to 3, more preferably 0.5 to 2
When it is in the range of 1, the running property and electromagnetic conversion characteristics are good, which is desirable.

The heat shrinkage of the film of the present invention at 200 ° C. for 10 minutes in at least one direction is preferably 5% or less, more preferably 2% or less. These mechanical properties,
It is preferable that the thermal properties of the laminated film are also satisfied when laminated.

Next, a method for producing the film of the present invention will be described, but the method is not limited to this.

First, an aromatic polyamide, but when it is obtained from an acid chloride and a diamine, it is used in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF). , Solution polymerization or interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride is by-produced.When neutralizing this, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate and lithium carbonate, and ethylene Oxide, propylene oxide, ammonia,
Organic neutralizing agents such as triethylamine, triethanolamine, diethanolamine are used. The reaction between isocyanate and carboxylic acid is carried out in the presence of a catalyst in an aprotic organic polar solvent.

These polymer solutions may be directly used as a film forming stock solution, or the polymer may be isolated once and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to prepare a film forming stock solution. Good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (value measured at 30 ° C. in a solution of 0.5 g of polymer in 100 ml of sulfuric acid) is 0.
It is preferably 5 or more.

Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride and lithium nitrate may be added as a dissolution aid to the stock solution for film formation. The polymer concentration in the stock solution for film formation is preferably about 2 to 40 wt%.

On the other hand, a solution of aromatic polyimide or polyamic acid is obtained as follows. That is, polyamic acid is N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DM).
It can be prepared by reacting a tetracarboxylic acid dihydrate with an aromatic diamine in an aprotic organic polar solvent such as F). The aromatic polyimide can be prepared by heating a solution containing the above polyamic acid or adding an imidizing agent such as pyridine to obtain a polyimide powder, which is dissolved again in a solvent. Polymer concentration in the film forming solution is 5
About 40 wt% is preferable.

The method for adding particles includes a method in which the particles are sufficiently slurried in a solvent in advance and then used as a solvent for polymerization or a solvent for dilution, or a method in which they are directly added after preparing a film-forming stock solution.

The stock solution for film formation prepared as described above is formed into a film by a so-called solution film forming method. Solution casting methods include dry-wet methods, dry methods, and wet methods.

When a film is formed by a wet method, the stock solution is filtered and then extruded directly from a die into a film forming bath, or once extruded onto a support such as a drum or a belt, and the whole support is placed in a wet bath. The method of introduction is adopted. This bath is generally composed of an aqueous medium, and may contain an organic or inorganic solvent or an inorganic salt in addition to water. The bath temperature is usually 0 to 1
It is used at 00 ° C., and the salts and solvents contained in the film are extracted by passing it through a wet bath. The time required to pass through these wet baths is 10 seconds to 30 minutes, depending on the thickness of the film. Further, if necessary, the film is stretched in the longitudinal direction. Then, drying and heat treatment are performed, but these treatments are generally performed at 200 to 500 ° C. for a total of 1
Seconds to 30 minutes. In this process, transverse stretching is carried out if necessary.

When a film is formed by a dry-wet method, the stock solution is extruded from a spinneret onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer until the thin film has self-holding property. To do. Drying conditions are room temperature to 3
It is within the range of 00 ° C. and 60 minutes. The film which has undergone the dry process is peeled from the support and introduced into the wet process, desalting and solvent removal are carried out in the same manner as in the above-mentioned wet process, and further stretched, dried and heat-treated to obtain a film.

When the dry process is adopted, the film which is dried on a drum, an endless belt or the like and has a self-holding property is peeled from these supports and stretched in the longitudinal direction of the film. . Further, drying for removing the residual solvent, stretching, and heat treatment are performed, and these treatments are performed at 200 to 500 ° C. for 1 second to 30 minutes.

The film formed as described above is stretched in the film-forming process so that the mechanical properties are within the range of the present invention. The stretching ratio is 0.8 to 8.0 in terms of areal magnification.
(Area magnification is defined as a value obtained by dividing the area of the film after stretching by the area of the film before stretching. 1 or less means relaxing.), And more preferably 1.1 to. It is 5.0. Further, it is effective to rapidly cool the film after stretching or heat treatment, and it is effective to cool the film at a rate of 100 ° C./sec or more.

The film of the present invention may be a laminated film. For example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two, and different particles are added, respectively, and then laminated. The same applies to the case of three or more layers.
As a method of stacking these, there are known methods such as stacking in a die, stacking in a composite tube, and a method in which one layer is once formed and then another layer is formed thereon.

[0049]

EXAMPLES The methods of measuring physical properties and evaluating effects of the present invention are as follows.

(1) Surface Roughness (Centerline Average Roughness, Ra) The surface roughness was measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions are as follows, and the average value of 20 measurements was taken as the surface roughness.

Stylus tip radius: 0.5 μm Stylus load: 5 mg Measurement length: 1 mm Cutoff value: 0.08 mm or 0.008 mm (2) F-1 value Instron type tensile tester Use, 25
It was measured at 60 ° C and 60% RH. The test piece is 10 mm wide and 5
0mm length, pulling speed is 10% / min or 1000%
/ Min.

(3) Scratch resistance A film was slit into a tape having a width of 1/2 inch, and a single blade was pressed perpendicularly to the film surface.
Run for 200m with 0mm pushed in (running tension:
100 g, traveling speed: 250 m / sec). At this time, the height of the shavings on the surface of the film attached to the tip of the single blade was read with a microscope and used as the shaving amount (unit: μm). This scraping amount is 60
When it was less than μm, it was evaluated as ◯, and when it exceeded 60 μm, it was evaluated as x.

(4) Electromagnetic conversion characteristics The film coated with the magnetic layer was slit into a 1/2 inch width and incorporated into a VTR cassette to obtain a VTR tape. Chroma S / N was measured from a 100% chroma signal by a television test waveform generator using a household VTR on this tape with a color video noise measuring instrument. The evaluation was made based on a commercially available tape.

(5) Runnability A slit running tape having a width of 1/2 inch was used as a tape runnability tester model SFT-700 (manufactured by Yokohama System Laboratory Co., Ltd.). The friction coefficient at the 50th pass was determined by the following equation after running in an atmosphere of 40 ° C. and 80% RH.

ΜK = 0,733 log (T ₂ / T ₁ ) where T ₁ is the inlet tension and T ₂ is the outlet tension. The guide diameter is 6 mmφ, the guide material is polyoxymethylene (with a surface roughness of about 20-40 nm), and the winding angle is 9
The angle is 0 °, the running speed is 3.3 cm / sec, and the repeating stroke is 15 cm. The μK obtained by this measurement is 0.
When it was 35 or less, the runnability was judged to be good, and when it exceeded 0.35, the runnability was judged to be bad. This μK is a critical point that affects the handling property when processing a film for a magnetic recording medium, a capacitor, packaging, and the like.

The present invention is described below based on examples, but the invention is not limited thereto.

Example 1 N-methylpyrrolidone (NMP) was mixed with 90 mol% of 2-chloroparaphenylenediamine as an aromatic diamine component and 10 mol% of 4,4-diaminodiphenyl ether. Dissolve and add 100 mol% of 2-chloroterephthalic acid chloride to this,
The polymerization was completed by stirring for a period of time. This was neutralized with lithium hydroxide to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight and a viscosity of 3000 poise. Add 0.1μ to this solution
0.5 wt% of spherical silica of m was added to the polymer.

This polymer solution was passed through a 10 μm-cut filter, cast on a belt, heated with hot air at 180 ° C. for 2 minutes to evaporate the solvent, and a film having self-supporting property was continuously formed from the belt. Peeled off. Next, the film was introduced into a water tank, the residual solvent and the inorganic salt generated by neutralization were extracted with water, and the moisture was dried and heat-treated with a tenter to obtain an aromatic polyamide film having a thickness of 9 μm. In the meantime, the film was stretched 1.2 times in the longitudinal direction and 1.3 times in the width direction, and after heat treatment at 280 ° C. for 1.5 minutes,
It was rapidly cooled at a rate of 120 ° C / sec.

[F-1] ₁₀₀₀ value of this film is 13k
g / mm ² , [F-1] ₁₀ / [F-1] ₁₀₀₀ = 0.92
Met. The [Ra] _0.08 value of this film is 0.006
and [Ra] _0.008 / [Ra] _0.08 = 0.85. Next, the abrasion resistance, running property, and electromagnetic conversion characteristics of this film were measured and found to be good.

Example 2 The polymer solution before addition of particles obtained by the same method as in Example 1 was divided into two parts, and spherical silica of 0.2 μm was added to one of them in an amount of 1.0 wt% per polymer (polymer solution I). . On the other hand, 0.3 wt.
Added (polymer solution II). Each of these two polymers was passed through a filter with a cut of 10 μm, and then a polymer II was laminated on the base layer portion and a polymer I was placed on the double-sided surface layer laminated portion by a three-layer composite pipe, and cast on a belt. Example 1 below
An aromatic polyamide film was prepared in the same manner as in (1).

[F-1] ₁₀₀₀ value of this film is 13k
g / mm ² , [F-1] ₁₀ / [F-1] ₁₀₀₀ = 0.92
Met. The [Ra] _0.08 value of this film is 0.008
μm, [Ra] _0.008 / [Ra] _0.08 = 0.72. The abrasion resistance, running property, and electromagnetic conversion characteristics of this film were measured, and it was very good.

Example 3 Paraphenylenediamine corresponding to 50 mol% as an aromatic diamine component and 4,4-diaminodiphenyl ether corresponding to 50 mol% were dissolved in dimethylacetamide (DMAc). Pyromellitic dianhydride corresponding to 100 mol% was added and polymerized to obtain a polyamic acid. This was divided into two, and 1.0 wt% of spherical silica of 0.1 μm was added to one of them (polymer solution III
), And on the other hand, 0.5 wt% of 0.2 μm spherical silica was added to the polymer (polymer solution IV). These two polymers were laminated in the same manner as in Example 2 so that the polymer solution IV was placed on the film base layer portion and cast on a belt. This was dried with hot air at 180 ° C. until it had self-holding property, further continuously peeled from the belt, heat-treated with a tenter at 420 ° C., and then rapidly cooled at a rate of 120 ° C./sec. The draw ratio was 1.1 times for both MD and TD, the thickness was 9 μm, and the [F-1] ₁₀₀₀ value of this film was 8 kg / mm ² , [F
−1] ₁₀ / [F-1] ₁₀₀₀ = 0.91. The [Ra] _0.08 value of this film is 0.007 μm, and the [Ra]
_{It was 0.008} / [Ra] _0.08 = 0.76. The abrasion resistance, running property, and electromagnetic conversion characteristics of this film were measured, and it was very good.

Comparative Examples 1 to 4 Polymer solution II similar to that in Example 2 and polymer solution V in which silica particles to be added were variously changed as shown in Table 3 were prepared in the same manner as in Example 2 to prepare polymer solution II as a base layer. Then, the aromatic polyamide film was laminated in the same manner as in Example 1 so that the aromatic polyamide film was obtained.

In Comparative Examples 1 and 3, the particle diameter and content contained were less than the range of the present invention, so the surface was too smooth and the running property of the film was very poor.

In Comparative Examples 2 and 4, the particle diameter and content contained exceeded the range of the present invention, so [Ra] _0.08 was large, and the running property was good, but the abrasion resistance and electromagnetic conversion were good. The characteristics were very poor.

Comparative Example 5 A polymer solution I similar to that of Example 2 and a polymer solution VI containing 0.1 wt% of silica particles having a particle size of 6 μm were added in the same manner as in Example 2, and polymer I was added to the surface layer portion on both sides of the film. Then, an aromatic polyamide film was prepared in the same manner as in Example 1. This film had good running properties and abrasion resistance, but had a large undulation on the film surface and had very poor electromagnetic conversion characteristics.

[0067]

[Table 1]

[0068]

[Table 2]

[0069]

[Table 3]

[0070]

The film of the present invention is obtained by adding particles to an aromatic polyamide or an aromatic polyimide. If at least one surface of the film is within the surface property range of the present invention, the film is processed at the time of processing the film, or When used as a magnetic tape or the like, the running property, abrasion resistance, and electromagnetic conversion characteristics are good, and the productivity and quality can be improved.

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Claims (1)

[Claims] 1. A film comprising an aromatic polyamide or an aromatic polyimide, wherein the film has a tensile rate of 1000% / min in at least one direction.
%, The film strength when stretched is 6 kg / mm ² or more, and the center line average roughness [Ra] _{0.08 of} at least one surface measured at a cutoff value of 0.08 mm is 0.001 to 0.001.
Center line average roughness [Ra] _0.008 and [Ra] _0.08 measured at a cutoff value of 0.008 mm in the range of 0.01 μm.
Is a base film for a magnetic recording medium, characterized in that 0.5 ≦ [Ra] _0.008 / [Ra] _0.08 ≦ 0.9 ...