JP3484844B2 - Magnetic recording media - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, there is known a magnetic recording medium comprising a polyester film provided with an oxide coating type magnetic layer or a metal coating type magnetic layer (for example, Japanese Patent Laid-Open No. 61-26933). JP-A-60-66319.
Issue Bulletin). Further, for the purpose of increasing the recording capacity per cassette, a proposal using an aromatic polyamide film as a base material of a magnetic recording medium is disclosed in JP-A-58-16865.
No. 5, JP-A-62-112218 and the like. However, the processing or use environment of the recording medium is diversified, and due to an increase in opportunities for outdoor use, a magnetic recording medium having stable performance even under high temperature and high humidity is demanded. However, the above-mentioned polyester film-based magnetic recording medium is very vulnerable to changes in the thermal environment. On the other hand, aromatic polyamide is said to be suitable as a base material for high density magnetic recording media because it has high rigidity and good heat resistance.

By the way, an aromatic polyamide structurally has a carboxyl group or an amino group as a terminal functional group unless special treatment is performed. A salt of an alkali metal or an alkaline earth metal, for example, is used as a neutralizing agent or a solubilizing agent when polymerizing an aromatic polyamide or forming an aromatic polyamide film. The terminal functional group is chemically active, and especially the carboxyl group is likely to form a metal salt.

Although these metal salts have not been a problem for conventional magnetic recording media, for example, adverse effects such as corrosion are likely to occur in high density recording magnetic recording media having a metal vapor deposition type magnetic layer formed thereon. .

Further, the metal ions formed in the film and the metal salt formed at the terminal of the aromatic polyamide have a strong affinity for moisture in the atmosphere, and cause dimensional changes such as swelling due to moisture absorption and elongation of the tape. Or it interferes with the formation of the vapor deposition layer. This is a fatal phenomenon in a magnetic recording medium for high density recording having a high track density.

As a means for solving this problem, for example, JP-A-3-259921 proposes to use a carbodiimide compound or a monocarboxylic acid chloride for end-capping. However, a large amount of the unreacted compound remains in the film, which exudes and the magnetic layer peels off. Further, this method is effective with polyparaphenylene terephthalamide, which requires a neutralization step after film formation, but still considerable metal ions remain.

[0007]

In recent years, due to an increase in the use of video cameras outdoors, a demand for miniaturization and a long recording time, and for use as an external memory of a computer, they are thin and harsh. There is an increasing demand for magnetic recording media having excellent durability under the conditions.

However, the above-mentioned polyester film-based magnetic recording medium has no problem at room temperature and normal humidity, but when used under high temperature and high humidity conditions, the running property and output characteristics are deteriorated, and in repeated running. The problem is that dropouts occur. It is considered that this is because the heat resistance and moisture resistance of the base film are insufficient, or the surface properties and running properties are insufficient.

Further, although aromatic polyamide is promising, the reliability is impaired due to corrosion of the magnetic layer due to residual metal ions and dimensional fluctuation due to moisture absorption.

The present invention solves the above problems, and sets the amount of metal ions and the dimensional change rate at prescribed values without impairing the excellent heat resistance and high rigidity of aromatic polyamides, thereby achieving high temperature and high humidity. It is an object of the present invention to provide a magnetic recording medium which is excellent in stable running property and output characteristic at the same time and is also excellent in durability.

[0011]

Means for Solving the Problems The inventors of the present invention have made extensive studies on a method for controlling the amount of metal ions contained in a polymer in order to solve the above-mentioned problems, and have made a constitution of the polymer or an amount of terminal functional groups at the time of polymerization. It was found from the knowledge of the preparation and film forming method that the amount of metal ions contained in the film can be greatly reduced, and the present invention has led to the present invention which is particularly suitable for high density magnetic recording after intensive studies.

That is, the present invention is a magnetic recording medium comprising a base film made of an aromatic polyamide or an aromatic polyimide and a magnetic layer provided on one side thereof, wherein the base film has a Young's modulus in at least one direction of 900 kg. / Mm
2 or more, the dimensional change rate at 100 ° C. under load is 2% or less, the metal ion contained in the base film is 10 ppm or less, and the terminal carboxyl group concentration contained in the base film is The magnetic recording medium is characterized in that it is 7 milliequivalents / kg or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide used in the present invention means the following general formula (I) and / or general formula (I
I) General formula (I)

[Chemical 1] General formula (II)

[Chemical 2] (Here, Ar ₁ , Ar ₂ and Ar ₃ are aromatic nuclei, and R, R ′ and R ″ are halogen groups, nitro groups, cyano groups, alkyl groups having 1 to 4 carbon atoms, and C 1 to 3 carbon atoms. A functional group selected from an alkoxy group and a trialkylsilyl group,
l and m are numbers 0 or more that do not become 0 at the same time, and n is an arbitrary positive number. ), The repeating unit represented by the general formula (I) and / or the general formula (II) is 50
Those containing at least mol% are preferable, and those containing at least 70 mol% are more preferable.

Here, Ar ₁ , Ar ₂ and Ar ₃ are, for example, those represented by the general formula (III)

[Chemical 3] And the like, X, Y is _{-O -, - CH 2 -,} - CO
_{-, - SO 2 -, -} S -, - C (CH 3) 2 - is chosen from such, but is not limited thereto.

From the viewpoint of characteristics, a polymer in which the above-mentioned aromatic ring is in the para position, that is, a divalent bond is bound coaxially or in parallel, occupies 50% or more, preferably 75% or more of the total aromatic ring. It is preferable because the film has high rigidity and good heat resistance.

The aromatic polyamide of the present invention contains the repeating unit represented by the general formula (I) and / or the general formula (II) in an amount of 50 mol% or more, and less than 50 mol% is another repeating unit. May be copolymerized or blended.

Further, in the general formula (III), an aromatic nucleus having a bond of X or Y can improve stability and film-forming property of a polymer solution and is preferably used, but if too much, it may cause deterioration of physical properties. , Preferably 5 to 5 of the raw material components
It is preferable to use it in the range of 0%, more preferably 7 to 30%.

It is important that the aromatic polyamide of the present invention can complete the polymerization as a uniform solution. In the present invention, as will be described later, there is a weak point in increasing the degree of polymerization in order to make a specific regulation on the ratio of charged raw materials, and in a system where a polymer is once formed as a precipitate, a sufficient degree of polymerization that can satisfy the mechanical performance of the present invention. Difficult to do. Further, in such a system, it is necessary to use sulfuric acid or the like as a film forming solution, and it is extremely difficult to reduce the amount of metal ions as described above.

As a means for improving the solubility of the aromatic polyamide, some of the hydrogen atoms on these aromatic rings are
In the general formula (I) and / or the general formula (II), R,
A halogen group (especially chlorine) represented by R'and R ",
Substitution with a substituent such as a nitro group, an alkyl group having 1 to 4 carbon atoms (especially a methyl group), and an alkoxy group having 1 to 3 carbon atoms is preferably performed. Further, use of a compound having a bond represented by X or Y in the general formula (III) is also preferably carried out. Furthermore, Ar ₁ , Ar ₂ and A
It is also preferable to use a meta or ortho-oriented aromatic nucleus as r ₃ . The above-mentioned means may be used alone or in combination. However, the latter two methods also have the effect of lowering the mechanical performance as described later,
It can be used within a range that does not impair the object of the present invention.
In the method of introducing a substituent into the aromatic nucleus, the values of l, m and n in the general formula (I) or the general formula (II) are arbitrary as long as the polymerization can be completed as a uniform solution.
Since this method has a good affinity for a commonly used solvent, it is preferably used because it effectively acts on desorption of metal ions when forming a film from a polymer solution, and at the same time, lowers the moisture absorption rate of the base film. In order to prevent dimensional fluctuation due to swelling and swelling, in the general formula (I), it is practical that l + m is 1 or more and 4 or less, preferably 2 or more and 4 or less and l> 0 and m> 0. . l + m
When the value exceeds 5, the film becomes brittle, which is not preferable. In the general formula (II), it is practical that n is 0.5 or more and 2 or less, preferably 1 or more and 2 or less. Also,
Among the substituents that can be introduced, the substituents that are preferably used include chlorine, methyl group and methoxy group because they have almost no deterioration in physical performance, and chlorine is more preferable because it has excellent heat resistance. An unnecessarily bulky functional group is rather unsuitable for the purpose of the present invention since it causes an increase in the coefficient of humidity expansion.

The aromatic polyimide in the present invention is one having at least one aromatic ring and one imide ring in the repeating unit of the polymer and is represented by the general formula (IV) and / or the general formula (V). The content of repeating units is preferably 50 mol% or more, more preferably 70 mol% or more.

General formula (IV)

[Chemical 4] General formula (V)

[Chemical 5] 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 an aromatic tetracarboxylic acid or its anhydride.
The following are typical examples.

[0022]

[Chemical 6] Wherein Z is _{-O -, - CH 2 -,} - CO -, - SO
_{2 -, - S -, -} C (CH 3) 2 - is chosen from such,
It is not limited to this.

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

[Chemical 7] And the like, X, Y is _{-O -, - CH 2 -,} - CO
_{-, - SO 2 -, -} S -, - C (CH 3) 2 - is chosen from such, but is not limited thereto. Further, a part of hydrogen atoms on these aromatic rings is a substituent such as a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 4 carbon atoms (especially a methyl group), an alkoxy group having 1 to 3 carbon atoms, and the like. And those in which hydrogen in the amide bond constituting the polymer is replaced by another substituent.

The metal ion concentration contained in the base film used in the magnetic recording medium of the present invention is 10 ppm or less.
Is important . The metal ion referred to in the present invention is an ion of an element having electric conductivity as a simple substance, and includes both a typical element and a transition element, but in particular, IA group,
The influence of IIA group and IIIA group elements, especially the influence of IA group element is large. If the residual amount of these metal ions is more than 10 ppm, the dimensional variation due to moisture absorption is large and the recording / reproducing property is deteriorated. In addition, it is not suitable for long-term use because it deteriorates the components of the magnetic layer.

The humidity expansion coefficient of the substrate film used for the magnetic recording medium of the present invention is preferably 1.3 × 10 ^-5 or less, more preferably 1.2 × 10 ^-5 or less. This number is 1.
If it exceeds 3 × 10 ⁻⁵ , it may cause a track shift due to a change in use environment, and the recording / reproducing characteristics are easily damaged.

For this purpose, further, it is not possible to substitute a hydrogen atom in the amide bond constituting the polymer with another substituent or to use a monomer having a relatively large molecular weight in order to reduce the amide group density. It is valid. In particular, introduction of a biphenyl structure, a naphthyl structure, and a terphenyl structure is preferably carried out. Further, in the case where the same component has different aromatic nuclei, for example, the phenyl structure and the biphenyl structure are introduced in the amine component, the film forming property is also improved. Is particularly preferable.

The aromatic polyamide used in the magnetic recording medium of the present invention may be blended with a lubricant, an antioxidant and other additives so long as the physical properties of the film are not impaired.

In the magnetic recording medium of the present invention, the tensile Young's modulus E20 of the base film at 20 ° C. and relative humidity of 60% in at least one direction is E 20 ≧ 900 kg / mm ² ,
Good Mashiku is E20 ≧ 1000kg / mm ^2. As for the direction of tensioning, it does not matter if the longitudinal direction or the width direction is tempered. The degree of tensioning is not particularly limited, but in consideration of characteristics such as elongation and tear resistance, the tensile Young's modulus E in the longitudinal direction E
MD and tensile Young's modulus ETD in the width direction are 0.5 ≦ EMD / E
It is practical that the range of TD ≦ 2. Since the magnetic recording medium of the present invention is used in a thin film in response to the demand for thinning of the magnetic recording medium for high density recording,
Alternatively, it is required to have a high Young's modulus (E20 ≧ 900 kg / mm ² ) in order to withstand the tension applied during stop / start. If the Young's modulus is lower than this range, the tape is elongated and the recording / reproducing property is deteriorated. In addition, since the base material film has a high Young's modulus (E20 ≧ 900 kg / mm ² ), it can withstand the tension applied during the formation of the magnetic recording medium such as the coating layer forming step and the back coat layer forming step, and also in processing. It is advantageous.

In the base film used in the magnetic recording medium of the present invention, particles can be preferably contained in order to secure running stability.

The type of such particles is not particularly limited, but for example, SiO ₂ , TiO ₂ , TiN, A
Examples thereof include inorganic particles and organic particles such as l ₂ O ₃ , ZrO ₂ , zeolite, and other fine metal powders.

The content of the particles contained in the base film is 0.01-5% by weight, preferably 0.05-3.
% By weight. If the content of the particles is less than the above range, it does not contribute to the improvement of the running property, and if it is more than the above range, the physical properties of the film are deteriorated and the abrasion resistance and the electromagnetic conversion characteristics are deteriorated.

The average primary particle size of the particles contained in the base film is 5 to 250 nm, preferably 10 to 10 nm.
It is 0 nm. If the average primary particle size is larger than the above range, the abrasion resistance is poor, and if it is smaller than the above range, the scratch resistance is poor.

Due to the particles thus contained, in the base film used in the magnetic recording medium of the present invention, the surface of the surface on which the magnetic layer is provided has a fine projection height of 3 to 200 nm, preferably 5 to 100 nm, and a diameter of Those having a diameter of 0.01 μm or more are preferably present at a density of 10 ⁴ to 10 ⁸ pieces / mm ² . By using the substrate film having the above-mentioned surface characteristics as the magnetic recording medium, the contact with the magnetic head can be made smooth, and the drop of the electromagnetic conversion characteristics due to the dropout or the decrease of the S / N ratio can be prevented, and the guide roller can be prevented. Alternatively, the contact area between the magnetic head and the tape is small, and the hardness balance is appropriately maintained, so that the basic running property and durability are extremely good.

The present invention is a magnetic recording medium in which a magnetic layer is provided on one surface of the base film.

As the method for forming the magnetic layer, there are a dry method such as a wet method in which a ferromagnetic powder is used as a magnetic paint by using various binders and applied on a base film, a vapor deposition method, a sputtering method, an ion plating method, and the like. Although not particularly limited, a wet method will be described here as an example.

The type of magnetic powder to be a magnetic material is not particularly limited, but ferromagnetic powder such as iron oxide, chromium oxide,
Fe, Co, Fe-Co, Fe-Co-Ni, Co-N
i and the like are preferably used.

The magnetic powder can be made into a magnetic paint by using various binders, but thermosetting resin binders and radiation curing binders are preferable, and other additives such as dispersants, lubricants and antistatic agents are used. May be.
For example, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate can be used.

The base film of the magnetic recording medium of the present invention can be used not only as a single layer film but also as a laminated film. In the case of a laminated film, the base film and the base layer portion (film constituting portion other than the laminated base film of the present invention) of the magnetic recording medium of the present invention may be the same kind or different. The base layer portion may also contain particles in at least one layer, the type of particles,
It is desirable to use the average primary particle diameter and content of the particles that are preferably used in the present invention. When the diameter of the particles in the base layer portion is larger than the diameter of the particles in the laminated base material film of the present invention, it is possible to impart an appropriate waviness to the base material film surface and further improve tape running property. Is desirable.

The thickness of the substrate film in the magnetic recording medium of the present invention is preferably 0.5 to 50 μm, more preferably 1 to 20 μm, and further preferably 2 to 10 μm. It is desirable because excellent running properties and electromagnetic conversion characteristics are realized.

In the magnetic recording medium of the present invention, the dimensional change rate at 100 ° C. for 10 minutes under load of the base film is 2% or less, preferably 1% or less. When the content is 2% or less, the dimensional change of the tape under temperature change or tension can be reduced, and good electromagnetic conversion characteristics that can withstand high density can be secured.

The elongation of the substrate film in the magnetic recording medium of the present invention is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, since the tape has appropriate flexibility.

When the aromatic polyamide or aromatic polyimide film used in the magnetic recording medium of the present invention is extracted with methylene chloride, the extraction residue has a weight ratio of 0.
It is preferably 2% or less. If a lot of low molecular weight components that can be extracted with methylene chloride remain in the film, these components will precipitate and become sticky on the surface of the magnetic recording medium when used for a long time in a harsh environment. As a result, it becomes easy to wind around the rollers, etc., resulting in deterioration of recording / reproducing characteristics and running performance.

It is preferable that these characteristics are also satisfied in the laminated film when laminated.

In order to obtain the magnetic recording medium of the present invention, the steps of polymerizing and forming the base film are important.
Examples of the method for obtaining the aromatic polyamide include a low temperature solution polymerization method, an interfacial polymerization method, a melt polymerization method, and a solid phase polymerization method, and the solution system polymerization is suitable for the present invention.

In order to further clarify the effects of the present invention, a case of obtaining from acid chloride and diamine as a low temperature solution polymerization method will be described below as an example.

As the polymerization solvent, known solvents such as N-methylpyrrolidone (NMP) and dimethylacetamide (D
An aprotic organic polar solvent such as MAc) or dimethylformamide (DMF) is used. At this time, impurities such as water in the polymerization solvent must be removed as much as possible, and the water content is 200 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm or less. Further, lithium chloride, lithium bromide, calcium chloride or the like may be added as a dissolution aid. Then the diamine and acid chloride are added. In the case of aromatic polyamide, the equivalence of diamine and acid chloride is very important for increasing the degree of polymerization, but in order to suppress the formation of terminal carboxyl groups, the ratio of acid chloride to diamine component is 98.5. % ~ 95
%, Preferably between 98% and 96%.

The concentration of the carboxyl group is 7 milliequivalents / kg or less, preferably 5 milliequivalents / kg or less. When the carboxyl group concentration exceeds this range, the adsorption of metal ions or the expansion due to moisture absorption is large and it is difficult to achieve the object of the present invention.

Although the acid chloride is often decomposed due to moisture and other factors, the purity of the acid chloride used in the present invention is preferably 99.9% or more.

Further, it is preferable to use a reaction vessel capable of stirring as efficiently as possible.

When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride is produced as a by-product. When neutralizing this, an inorganic solvent such as calcium hydroxide, calcium carbonate or lithium carbonate is used. Solubilizers and organic neutralizing agents such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine and diethanolamine are used. The latter organic neutralizing agent is effective in reducing the amount of metal ions in the polymer solution and is preferably used, but if it remains in the film, it induces various problems such as oozing, and caution is required in its use. is there.

The polymer solution obtained by the above-described method has a high degree of polymerization and a low degree of dispersion as a result of uniform polymerization, and the value obtained by dividing the number average molecular weight by the weight average molecular weight is The range of 1.2 or more and 3.5 or less, which is suitable for the present invention, is more preferably 1.2 or more and 2 or less.

These polymer solutions may be used as a film forming stock solution as they are, 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. Further, the polymer concentration is preferably about 2 to 40% by weight.

In order to obtain the aromatic polyamide or aromatic polyimide film of the present invention, the intrinsic viscosity of the polymer (0.5 g of the polymer is added to 100 ml of a solution in sulfuric acid to prepare a solution of 3 g).
The value measured at 0 ° C.) is preferably 0.5 or more.

The method of adding particles is not particularly limited, but in order to adjust the degree of coagulation and suppress the appearance of coarse projections, for example, the particles are dispersed in advance in a solvent of 10 poise or preferably 1 poise or less. Can be mentioned. The solvent is preferably the same as that used for film formation, but other solvents may be used unless particularly adverse effects are observed. Further, additives such as a dispersion aid may be used in these solvents within a range that does not adversely affect dispersion. For dispersing the particles, a stirring disperser, a ball mill, an ultrasonic disperser or the like is used, and the particle diameter and the degree of aggregation are adjusted within the scope of the present invention.

The dispersed particles are mixed with the above-mentioned polymer solution, but in the case of mixing, they may be added to a solvent before polymerization, after polymerization, or at the time of preparing a polymer solution, and further just before casting. It is important that it is uniformly dispersed in the undiluted solution from the viewpoint of ensuring runnability.

The stock solution for film formation prepared as described above is formed into a film by a so-called solution film forming method. The solution film-forming method may be a dry-wet method, a dry method, a wet method, or the like, and the film may be formed by any method, but here, the dry-wet method will be described as an example.

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 a self-holding property. To do. Drying conditions are, for example:
Room temperature to 220 ° C, within 60 minutes, preferably room temperature to
It can be performed in the range of 200 ° C. Further, it is preferable to control the surface defect frequency of the drum and endless belt used in this drying step from the viewpoint of controlling coarse protrusions,
For example, the frequency of surface defects with a diameter of 30 μm or more is 0.001.
~ 0.02 pieces / mm ² , preferably 0.002-0.01
It should be 5 pieces / mm ² . The film after the dry process is peeled from the support and introduced into the wet process, desalting, desolventizing and the like are performed in the same manner as the above-mentioned wet method, and further stretching,
It is dried and heat-treated to form a film.

In this process, the wet process and the stretching / heat treatment process play important roles. The polymer prepared as described above has a reduced carboxyl group concentration, and also has a functional group in the aromatic nucleus to smoothly remove metal ions, but by controlling the wet process, a more suitable film can be obtained. can do.

Water may be used as a desolvent for the aromatic polyamide or aromatic polyimide of the present invention.
A mixed medium of water and an organic solvent can be preferably used.
At this time, the organic solvent is water-soluble, and preferably an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF) is preferable as in the polymerization solvent. If the temperature is 60 ° C. or higher, the purpose can be more easily achieved.

Further, a suitable stretching / heat treatment step gives a more ordered high-order structure and contributes to a decrease in the coefficient of humidity expansion. Stretching is a stretch ratio of 1.1 to 8.0 in terms of areal ratio (the areal ratio is defined as the value obtained by dividing the film area after stretching by the area of the film before stretching. 1 or less means relaxing). It is preferably within the range, more preferably 1.3 to 5.0 or 70% or more of the maximum draw ratio. At this time, it is effective to reduce the humidity expansion coefficient by taking a stretching ratio as large as possible. In addition, in order to increase the packing degree of the molecular chain and decrease the humidity expansion coefficient, 200 ° C to 500 ° C.
The heat treatment is preferably performed at a temperature of 250C, preferably 250C to 400C for a few seconds to a few minutes. Further, it is effective to gradually cool the film after stretching or heat treatment.
It is effective to cool at a rate of ° C / sec or less.

The base film used in the magnetic recording medium 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,
Known methods include, for example, stacking in a die, stacking in a composite tube, and a method of once forming one layer and then forming another layer thereon.

Next, a magnetic layer is formed on this film. The method of forming the magnetic layer can be performed by a known method, but in the case of a wet method, a method using a gravure roll is more preferable from the viewpoint of uniformity of the coating film. The drying temperature after coating is preferably 90 ° C to 150 ° C. The calendering step is preferably performed in the range of 25 ° C to 150 ° C.

Thereafter, a back coat layer may be provided on the surface opposite to the magnetic layer by a known method in order to further improve the running property.

Further, if necessary, the film having the magnetic layer formed thereon is cured and then slit to obtain the magnetic recording medium of the present invention.

Since the magnetic recording medium thus obtained can be made compact and thin, it is compact and can record a large amount of data.
In addition, since the dimensional change due to temperature and humidity is small, it is particularly suitable for digital recording materials such as digital tapes for computers. Further, since it is excellent in running property under high temperature and high humidity and electromagnetic conversion characteristics, it is suitable for outdoor use and can be suitably used for tapes for video cameras.

[0066]

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

(1) A metal ion amount film of 0.7 gram was precisely weighed and 550 in a platinum crucible.
It was incinerated by heating above ℃. The ash was dissolved in nitric acid and hydrofluoric acid, and the volume was adjusted to a constant volume with dilute nitric acid. This constant volume solution was quantified by ICP emission spectrometry or atomic absorption spectrophotometry. The unit ppm is μg / g. However, the part resulting from the addition of particles is excluded.

(2) Tensile Young's modulus The Young's modulus was measured using an Instron type tensile tester. The test piece is 10 mm wide and 50 mm long, and the pulling speed is 300 mm / min. A constant temperature and constant humidity tank was used for the sample preparation of E20, and the sample whose temperature and humidity had been adjusted for 48 hours was taken out from the tank and quickly measured.

(3) Dimensional change rate A load of 0.5 kg / mm ² was applied to the oven at a temperature of 100 ° C. for 10 minutes, and the temperature was returned to room temperature.

[0070]

[Formula 1] (4) Humidity expansion coefficient A thermomechanical analyzer manufactured by Rigaku Denki Co., Ltd. was installed in an environment in which the temperature was kept constant at 25 ° C. and the humidity could be controlled.
Measuring the dimensional change of the film in the region of 0% RH,
It was calculated by the following formula.

Humidity expansion coefficient = (dimensional change amount (mm)) /
((90-30) x test length (mm))

(5) The terminal carboxyl group concentration experiment was conducted in a nitrogen atmosphere. 0.2 g of a film from which free acidic components were removed with hot water was weighed, and 0.001N sodium hydroxide water / ethanol = 1/1 solution 25
ml was added, and the mixture was heated under reflux for 4 hours. Then, the polymer is filtered off and washed with ethanol, and the filtrate and this washing solution are mixed with 0.00
It was determined by titration with 1N hydrochloric acid.

(6) Extraction rate of methylene chloride 10 g of a film was weighed out and 2 using a Soxhlet extractor
Extracted for 4 hours. Then, the extract was evaporated to dryness with an evaporator, and the weight of the residue was calculated according to the following formula.

Extraction rate of methylene chloride = (residual weight (g) /
Film weight (g)) x 100

(7) Block error rate A magnetic coating material having the following composition was prepared on the surface of the obtained film which was not in contact with the metal belt during film formation, and a magnetic layer having a thickness of 2 μm was formed by a gravure roll. The magnetic coating was applied so as to obtain the above, and after curing, calendering was performed.

Magnetic powder (metal powder) 80 parts by weight PVC copolymer 20 parts by weight Polyurethane 10 parts by weight Curing agent 5 parts by weight Abrasive 5 parts by weight Toluene 100 parts by weight Methyl ethyl ketone 100 parts by weight The tape thus formed with a magnetic layer is used. It was slit into 1/2 inch and assembled into a cassette to prepare a sample. Then 1 kHz
Record the sinusoidal signal for 5 minutes. 80%, 90%
Every one month under the environment of RH, the reproduction was performed thereafter. At the time of reproduction, the error signal was counted, the number of errors per second was divided by the predetermined number of blocks to obtain, and the evaluation was made in the following three stages.

◎: more than 10 ^-4 ○: 10 ^-3 to 10 ^-4 x: less than 10 ^-3

(8) Using a tape running tester SFT-700 (manufactured by Yokohama System Laboratory Co., Ltd.), which was prepared by slitting a running film into a tape having a width of 1/2 inch, The friction coefficient was determined from the following formula by running in an atmosphere of 40 ° C. and 80% RH.

ΜK = 0.733 log (T2 / T1) where T1 is the inlet tension and T2 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
0 °, the running speed is 3.3 cm / sec, and the repeating stroke is 15 cm. When μK of the 10th pass obtained by this measurement is μK10 and μK of the 100th pass is μK100, the runnability is ○ when μK100 / μK10 is 0.8 or more and 1.2 or less. It was judged as sex x. In addition,
In order to avoid the influence of static electricity, the film was subjected to measurement after static elimination every time.

The present invention will be described below based on examples, but the present invention is not limited to these.

Examples 1 to 6 and Comparative Examples 1 to 3 However, the abbreviations shown in the raw material column are as follows. The number before each abbreviation symbol indicates the substitution site of the substituent. (Example: 3,3'-DMB: 3,3'-dimethylbenzidine) Aromatic diamine component: PA: Paraphenylenediamine CPA: Chloroparaphenylenediamine DMB: Dimethylbenzidine DOB: Dimethoxybenzidine DAE: Diaminodiphenyl ether acid chloride component: TPC: Terephthaloyl chloride IPC: Isophthaloyl chloride CTPC: Chloroterephthaloyl chloride

Example 1 N-methylpyrrolidone (NMP), 2-CPA corresponding to 80 mol% as an aromatic diamine component, and 20 mol%
4,4'-DAE corresponding to
2-CTPC corresponding to mol% was added and stirred for 2 hours to complete the polymerization. Neutralize this with lithium hydroxide,
An aromatic polyamide solution having a polymer concentration of 10% by weight and a viscosity of 2900 poise was obtained. Then, 2% by weight of silica particles having an average primary particle size of 16 nm and a Mohs hardness of 7 was added to this solution based on the polymer, and stirred to obtain a polymer solution.

This polymer solution was passed through a 5 μm-cut filter, cast on a SUS belt, heated with hot air at 180 ° C. for 2 minutes to evaporate the solvent, and a film having self-supporting property was formed on the belt. Was continuously peeled off. Then 60 ℃
Water / NMP ratio kept at 1/1, 2/1, 5 /
The film was introduced into a plurality of water tanks having a concentration ratio of 1 and 10/0 to extract the residual solvent and the inorganic salt, and the moisture was dried and heat-treated with a tenter to obtain an aromatic polyamide film having a thickness of 6 μm. Obtained. In the meantime, the film was stretched 1.2 times and 1.3 times in the longitudinal direction and the width direction, respectively.
After drying and heat treatment at 80 ℃ for 1.5 minutes, 20 ℃
It was gradually cooled at a rate of / sec.

The metal ion concentration of this film is 10 pp.
m, Young's modulus E20 1230 kg / mm ² , dimensional change rate 0.3%, humidity expansion coefficient 11 × 10 ^-6 , terminal carboxyl group concentration 4 meq / kg, methylene chloride extraction rate 0.2%. Hereafter, the ratio of the number average molecular weight / the weight average molecular weight was 1.9.

Next, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the running property were measured and it was good. Further, it was also good to measure the block error rate again after repeatedly running 100 times at 40 ° C.

Example 2 N-methylpyrrolidone (NMP), 3,3′-DOB corresponding to 80 mol% as an aromatic diamine component, and 20
4,4'-DAE corresponding to mol% was dissolved, 2-CTPC corresponding to 97 mol% was added thereto, and the mixture was stirred for 2 hours to complete the polymerization, and the film was stretched in the longitudinal direction of 1. Example 1 except for multiplying 1 times and 1.45 times in the width direction
An aromatic polyamide film having a thickness of 6 μm was obtained in the same manner as in.

The metal ion concentration of this film is 8 pp.
m, Young's modulus E20 is 1250 kg / mm ² , dimensional change rate is 0.2%, humidity expansion coefficient is 9 × 10 ^-6 , terminal carboxyl group concentration is 3 meq / kg, methylene chloride extraction rate is 0.2%. It was below.

Next, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the running property were measured by the above-mentioned methods, and it was good.

Example 3 3,3'-DMB corresponding to 50 mol% as an aromatic diamine component in NMP and 2-CP corresponding to 50 mol%
A was dissolved, 98 mol% of 2-chloroterephthalic acid chloride corresponding to 98 mol% was added thereto, and the mixture was stirred for 2 hours to complete the polymerization. An aromatic polyamide film having a thickness of 6 μm was obtained in the same manner as in Example 1.

The metal ion concentration of this film is 8 pp.
m, Young's modulus E20 is 1400 kg / mm ² , dimensional change rate is 0.1%, humidity expansion coefficient is 9 × 10 ^-6 , terminal carboxyl group concentration is 2 meq / kg, methylene chloride extraction rate is 0.1%. Met.

Next, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the running property were measured by the above-mentioned methods and the results were good.

Example 4 3,3′-DMB corresponding to 60 mol% as an aromatic diamine component in NMP and 3,4 ′ corresponding to 40 mol%
-Dissolve DAE, which corresponds to 96 mol% 2
-Chlorterephthalic acid chloride was added and stirred for 2 hours to complete the polymerization. An aromatic polyamide film having a thickness of 6 μm was obtained in the same manner as in Example 1.

The metal ion concentration of this film is 10 pp.
m, Young's modulus E20 is 900 kg / mm ² , and dimensional change rate is 0.
8%, humidity expansion coefficient 13 × 10 ^-6 , terminal carboxyl group concentration 2 meq / kg, methylene chloride extraction rate 0.
It was 2% or less.

When the film was used as a magnetic recording medium, a back coat layer having the following composition was further provided on the nonmagnetic surface. The coating material for the back coat layer has the following composition.

Carbon black 100 parts by weight PVC copolymer 20 parts by weight Polyurethane 50 parts by weight Toluene 200 parts by weight Methyl ethyl ketone 400 parts by weight For the tape or magnetic recording medium obtained from this film, the block error rate and running were performed by the method described above. The property was measured and was good.

Example 5 85% by mol of 2-CPA as an aromatic diamine component in NMP and 3,4'-DAE corresponding to 15% by mol of NMP
Was dissolved in the solution, and 3 mol ', 4, corresponding to 5 mol%
4'-biphenyltetracarboxylic dianhydride was added and stirred for 30 minutes, and after cooling 2-CT corresponding to 93 mol%
PC was added and the mixture was further polymerized for 2 hours to obtain a polyamic acid solution.

To this solution, 2 wt% of dry silica having a temporary particle size of 16 μm was added per polymer.

An aromatic polyamide film having a thickness of 6 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature of this polymer solution was changed to 420 ° C.

The metal ion concentration of this film is 7 pp
m, Young's modulus E20 is 1420 kg / mm ² , dimensional change rate is 0.2%, humidity expansion coefficient is 12 × 10 ^-6 , terminal carboxyl group concentration is 4 meq / kg, methylene chloride extraction rate is 0.2%. It was below.

Then, with respect to the tape or magnetic recording medium obtained from this film, the block error rate and the running property were measured by the above-mentioned methods, and the results were good.

Example 6 Polymerization was completed by the method of Example 1 except that propyne oxide and triethylamine were used instead of lithium hydroxide as the neutralizing agent, and a water bath was used instead of the organic solvent / water bath. Similarly obtained a film.

Almost no metal ions were detected in this film, Young's modulus E20 was 1250 kg / mm ² , dimensional change rate was 0.4%, humidity expansion coefficient was 12 × 10 ^-6 , and terminal carboxyl group concentration was 3 meq / kg, methylene chloride extraction rate was 0.3% or less.

Then, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the running property were measured by the above-mentioned methods, and the results were good.
When the runnability and the block error rate were measured again after running 100 times repeatedly at 40 ° C., it was a pass level, but it was lower than the initial level. In addition, some scratches were found on the tape, suggesting that it is not suitable for long-term use or applications requiring high reliability such as digital tape.

Comparative Example 1 The same polymer solution as in Example 1 was cut with a 5 μm filter.
After passing through, the film was cast on a SUS belt, heated with hot air at 200 ° C. for 5 minutes to evaporate the solvent, and the film having self-holding property was continuously peeled from the belt. Then, the residual solvent and the inorganic salt were extracted in a water tank kept at 70 ° C. for 1/3 of the extraction time in the example, and then an aromatic polyamide film having a thickness of 6 μm was prepared in the same manner as in Example 1. Obtained.

The metal ion concentration of this film is 120 p.
pm, Young's modulus E20 is 1200 kg / mm ² , dimensional change rate is 0.5%, coefficient of humidity expansion is 15 × 10 ^-6 , terminal carboxyl group concentration is 4 meq / kg, methylene chloride extraction rate is 0.3%. Met.

Then, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the runnability were measured by the above-mentioned methods, and the runnability was good, but the error frequency was a little bad. Also, 100 at 40 ° C
When the runnability and block error rate were measured again after repeated running, deterioration was recognized.

Comparative Example 2 100 mol% of PA corresponding to an aromatic diamine component was dissolved in NMP and cooled to -10 ° C. 10 to this
Polymerization was completed by adding TPC corresponding to 0 mol% and stirring for 2 hours while pulverizing the solid precipitated during the polymerization into small pieces. This solid slurry was precipitated in water, washed with water, and dissolved in concentrated sulfuric acid to obtain an aromatic polyamide solution. To this solution, dry silica having a primary particle size of 16 nm was added in an amount of 2 w per polymer.
t% was added. The polymer solution was passed through a 5 μm-cut filter and then cast on a gold-plated belt,
Keep until it becomes an isotropic solution under the atmosphere of% RH,
Then, it was introduced into a water tank for coagulation, the coagulated film was peeled off from the belt and washed with water, and then passed through a 0.1% caustic soda aqueous solution tank for neutralization, and then passed through a water tank. Then, an aromatic polyamide film having a thickness of 10 μm was obtained in the same manner as in Example 1.

The metal ion concentration of this film is 500 p.
pm, Young's modulus E20 is 1320 kg / mm ² , dimensional change rate is 0.3%, humidity expansion coefficient is 25 × 10 ^-6 , terminal carboxyl group concentration is 25 meq / kg, methylene chloride extraction rate is 0.2%. It was below.

Then, with respect to the tape or the magnetic recording medium obtained from this film, the block error rate and the running property were measured by the above-mentioned methods, and the running property was good, but the error frequency was rather poor. However, when the runnability and block error rate were measured again after running 100 times repeatedly at 40 ° C., further deterioration was recognized.

Comparative Example 3 N-methylpyrrolidone (NMP), 2-CPA corresponding to 70 mol% as an aromatic diamine component, and 30 mol%
And 4'-DAE corresponding to
IPC equivalent to mol%, 2-C equivalent to 50 mol%
TPC was added and stirred for 2 hours to complete the polymerization. Then, a polymer solution and an aromatic polyamide film having a thickness of 6 μm were obtained in the same manner as in Example 1. During this time, 1.2 times and 1.3 times respectively stretching in the longitudinal direction and width direction of the film,
After drying and heat treatment at 280 ° C for 1.5 minutes, 20
It was gradually cooled at a rate of ° C / sec.

The metal ion concentration of this film is 10 pp.
m, Young's modulus E20 is 780 kg / mm ² , dimensional change rate is 2.
2%, humidity expansion coefficient 16 × 10 ^-6 , terminal carboxyl group concentration 4 meq / kg, methylene chloride extraction rate 0.
It was 2% or less.

Next, the block error rate and running property of the tape or magnetic recording medium obtained from this film were measured by the above-mentioned methods. The runnability and the block error rate were fair, but deterioration was observed when the block error rate was measured again after repeatedly running 100 times at 40 ° C.

[0113]

[Table 1]

[0114]

INDUSTRIAL APPLICABILITY The present invention uses the above-mentioned base film made of an aromatic polyamide, and does not impair the excellent mechanical performance inherent to the aromatic polyamide, and is 100% under load.
The dimensional change rate at 2 ° C. is 2% or less, and the metal ions contained in the base film can be 10 ppm or less. Thus, a magnetic recording medium suitable for outdoor use can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-185507 (JP, A) JP-A-3-259912 (JP, A) JP-A-2-84328 (JP, A) JP-A-6- 180836 (JP, A) JP 8-339530 (JP, A) JP 62-112218 (JP, A) JP 8-134233 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 5/73

Claims (2)

(57) [Claims] 1. A magnetic recording medium comprising a base film made of aromatic polyamide or aromatic polyimide and a magnetic layer provided on one side thereof, wherein the base film has a tensile Young's modulus of at least one direction of 900 kg / mm ^2. And above, the dimensional change rate at 100 ° C. under load is 2% or less, and the metal ion contained in the base film is 10 % or less.
A magnetic recording medium characterized in that the concentration of the terminal carboxyl groups contained in the base film is 7 ppm or less and is not more than 7 ppm. 2. The magnetic recording medium according to claim 1, which has a coefficient of humidity expansion of 1.3 × 10 ⁻⁵ or less.