JP2000011363A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity by forming a magnetic layer on the surface of an aromatic polyamide film having equal to or below a specific slack quantity under a specific condition to prevent the deformation due to heat or the like to secure smoothness and to improve travelling property. SOLUTION: The deformation of the film caused by separating from a supporting body such as a drum at the time of vapor depositing the magnetic layer and the damage of the film caused by the poor contacting with a guide roll at the time of travelling are prevented by providing the magnetic layer on the surface of the aromatic polyamide film having <=60 mm, preferably <=30 mm slack quantity when 0.5 kg/mm2 weight is loaded on the 610 mm wide 2 m long film. And the generation of wrinkles caused by the sliding defect of the film at the time of vapor deposition is suppressed by controlling the friction coefficient of the surface of the non-magnetic layer opposed to the surface of the magnetic layer to <=2 and the deterioration of the magnetic properties is suppressed by controlling the 10 points average roughness of the film surface of the magnetic layer side to 1-100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a magnetic layer provided on an aromatic polyamide film having good heat resistance and flatness.

[0002]

2. Description of the Related Art Various applications of aromatic polyamide films are being studied by utilizing their excellent heat resistance and mechanical properties. In particular, para-oriented aromatic polyamides are superior to other polymers in mechanical properties such as rigidity and strength, and are therefore advantageous for thinning films or improving the strength of film base materials, such as printer ribbons, magnetic recording media, and capacitors. Applications such as solar cells and the like are being studied.

As a magnetic recording medium, JP-A-58-168655,
This is known from JP-A-62-112218. As a magnetic recording medium, Co, a coating type manufactured by applying a magnetic powder together with a binder to the surface of a film, a method such as vacuum evaporation, sputtering, or ion plating, may be used.
There is a metal thin-film type magnetic recording medium in which Ni, Cr, etc. are formed on a base film, and the latter is particularly expected to improve the recording density.

[0004]

As a method of manufacturing a magnetic recording medium, in the case of a metal thin film type, there is a method in which a film is continuously formed on a film in a vacuum by a method such as vacuum evaporation or sputtering. Various improvements have been made to the manufacturing process to improve productivity and magnetic properties.
As vapor deposition is performed at a high temperature, it is important to improve heat resistance and flatness of a film. In particular, in the production of a metal thin film type magnetic recording medium, if the flatness of the film is poor, the film floats up from a support such as a drum at the time of vapor deposition, and a problem that the film in that portion is thermally deformed occurs. Further, with the improvement of the running speed, unevenness of the running property occurs due to poor flatness, and there is a problem of deterioration of film characteristics such as damage to the film.

An object of the present invention is to solve the above-mentioned problems and to provide a magnetic recording medium using a film which is flat and can withstand an improvement in productivity by utilizing the excellent high rigidity and heat resistance of aromatic polyamide. And

[0006]

The present invention relates to an aromatic polyamide having a film thickness of 60 mm or less at the center when a load of 0.5 kg / mm ² is applied to a film of 610 mm width and 2 m length. A magnetic recording medium characterized in that a magnetic layer is provided on the surface of the film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide of the present invention preferably contains at least 50 mol% of repeating units represented by the following general formulas (I) and / or (II), more preferably at least 70 mol%. Is more preferred.

Formula (I)

Embedded image General formula (II)

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

Embedded image And the like, X, Y is _{-O -, - CH 2 -,} - CO -, - SO 2 -, -S-,
—C (CH ₃ ) ₂ — and the like, but is not limited thereto. Further, some of the hydrogen atoms on these aromatic rings may be substituted with a substituent such as a halogen group (especially chlorine), a nitro group, a C ₁ -C ₃ alkyl group (especially a methyl group), a C ₁ -C ₃ alkoxy group. And those in which the hydrogen in the amide bond constituting the polymer is substituted by another substituent. From the viewpoint of characteristics, those in which the above aromatic rings are bonded at the para position are 50% or more, preferably 7%, of the total aromatic rings.
A polymer occupying 0% or more is preferable because the film has high rigidity and good heat resistance. From the viewpoint of reducing the moisture absorption, a polymer in which a part of hydrogen atoms on an aromatic ring is substituted with a halogen group (particularly chlorine) and the aromatic ring is 30% or more of the whole is preferable.

A more preferred structure of the aromatic polyamide is as follows:

Embedded image (Where m and n are from 0 to 4) are at least 50 mol%, more preferably at least 70 mol%.

The aromatic polyamide of the present invention preferably contains at least 50 mol% of the repeating units represented by the general formula (I) and / or the general formula (II). Less than 50 mol% may be copolymerized or blended, and conductive particles, lubricants, antioxidants and other additives may be blended to such an extent that the physical properties of the film are not impaired.

The film of the present invention has a thickness of 1 μm or more and 20 μm or more.
μm or less is preferred. More preferably, 2 μm or more and 6 μm
It is as follows.

In the film of the present invention, when a load of 0.5 kg / mm ² is applied to a film having a width of 610 mm and a length of 2 m, the thickness of the film at the central portion needs to be 60 mm or less. Preferably it is 30 mm or less. If it is larger than 60 mm, in the case of vapor deposition, the film separates from the support on a support such as a drum, and problems such as deformation of the film by heat occur. Further, when the film is run, the contact with the guide roll becomes poor, and problems such as scratching of the film occur.

The film of the present invention has a surface (A) on which a magnetic layer is provided.
The friction coefficient of the nonmagnetic layer surface (referred to as surface B) different from that of the nonmagnetic layer (referred to as surface B) is preferably 2 or less, more preferably 1 or less. The lower limit is not particularly limited, but is preferably about 0.2. If the coefficient of friction is larger than 2, when wrinkles are formed on the support during vapor deposition, the film becomes less slippery, so that the wrinkles cannot be extended and the film is deformed by heat.

The ten-point average roughness Rz of the surface on which the magnetic layer is provided is
Is preferably 1 to 100 nm. More preferably, it is 2 to 50 nm. If it is larger than this, there is a concern that the magnetic properties may deteriorate.

The film of the present invention preferably contains particles in the film in order to maintain the surface roughness and the coefficient of friction. The types of particles include SiO ₂ , Ti
Inorganic particles such as O ₂ , Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ , carbon black, zeolite and other metal fine powders, silicon particles, polyimide particles, cross-linked copolymer particles, cross-linked polyester particles And organic polymers such as Teflon particles, but inorganic particles are more preferable from the viewpoint of heat resistance. The particle size is in the range of 0.01 to 5 μm, more preferably 0.05 to 2 μm. The content is preferably 0.005 to 10 wt%, and 0.01 to 5 wt%.
% Is more preferred.

The surface properties of the surface A and the surface B may be the same or different, but it is preferable to roughen the surface B especially in the case of a metal thin film type. The surface properties can be changed by a known method, for example, a method of applying particles and a binder to the surface of a film, a method of laminating with a die or a laminated tube, and the like. Further, one or more other layers may be provided between the layer A and the layer B.

The film of the present invention preferably has a heat shrinkage in the TD direction at 150 ° C. of 2% or less. More preferably 1%
It is as follows. If it exceeds 2%, the film is likely to be deformed by heat in the case of vapor deposition.

The Young's modulus of the film of the present invention is 700 kg / mm ² or more in the MD direction and 800 kg / mm ² in the TD direction.
mm ² or more, more preferably 1000 kg /
mm ² is preferred.

The elongation of the film of the present invention is preferably 10% or more, more preferably 20% or more, and still more preferably 3% or more.
If it is 0% or more, it is desirable because it has appropriate flexibility.

The film may be tensilized in the longitudinal direction or tensilized in the width direction. The degree of tensilization is not particularly limited, but considering characteristics such as elongation and tear resistance, the tensile Young's modulus EMD in the longitudinal direction and the tensile Young's modulus EtD in the width direction are 0.5 ≦ EMD / ETD ≦ 2. Is practical.

The moisture absorption of the film of the present invention is preferably 4% or less, more preferably 3% or less, and further preferably 2% or less.
% Or less. The smaller the moisture absorption, the smaller the dimensional change of the magnetic recording medium due to the change in humidity, and can maintain good electromagnetic conversion characteristics.

The magnetic recording medium of the present invention is obtained by providing a magnetic layer on the above-mentioned film.

The thickness of the magnetic layer is 2 μm or less, more preferably 1 μm or less. For short-wavelength recording, thinner is better, but if too thin, the output will decrease.
m or more. Ni, Cr, Fe, Co
And the like, and alloys thereof, but are not limited thereto.

Generally, it is preferable to provide a back coat layer as a magnetic recording medium. The thickness of the back coat layer is preferably 1 μm or less.

Further, a protective layer can be provided on the magnetic layer to improve durability. For example, it is a carbon layer, a lubricant layer, or the like, and can be provided alone or in combination of several kinds.

Next, the manufacturing method of the present invention will be described, but the present invention is not limited thereto.

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

These polymer solutions may be directly used as a stock solution for film formation, 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 stock solution for film formation. Is also good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (measured at 30 ° C. as a 100 ml solution of 0.5 g of polymer in sulfuric acid)
It is preferably 0.5 or more. In some cases, an inorganic salt, for example, calcium chloride, magnesium chloride, lithium chloride, lithium nitrate, or the like is added as a dissolution aid to the stock solution for film formation. The polymer concentration in the film forming stock solution is preferably about 2 to 40% by weight.

As a method for adding the particles, there is 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 a stock solution is directly added after preparing a stock solution.

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

When a film is formed by a dry-wet method, the undiluted solution is extruded from a die onto a support made of a material such as nickel, stainless steel, copper, titanium, hastelloy, tantalum or the like, a drum, an endless belt or the like to form a thin film. The solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. Drying conditions are preferably in the range of room temperature to 250 ° C and within 60 minutes, more preferably in the range of room temperature to 200 ° C.
When the drying temperature exceeds 250 ° C., voids are generated due to rapid heating, the surface is roughened, and a practical film cannot be obtained.

The film after the above-mentioned dry process is peeled from the support and introduced into the wet process to remove the solvent and impurities contained in the film. The bath in this step is generally composed of an aqueous medium, and may contain an organic solvent or an inorganic salt in addition to water. The water content is preferably 30% or more, more preferably 50% or more, and the bath temperature is 0 to 0%.
Used at 100 ° C.

The film after the wet process is further dried and stretched. Drying and stretching are performed at room temperature to 400 ° C., and the stretching ratio is 0.8 to 5.0 in area ratio (the area ratio 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 relaxation.) A more preferred stretching ratio is 1.1 to 3.0. Depending on the type of polymer, it may be better to stretch in a water-containing state, and it may be stretched at 80 ° C. or lower, which is close to room temperature.

In order to further improve the flatness in the TD direction, it is preferable to maintain the stretching temperature unevenness in the TD direction at 2% or less of the average temperature. The film is cooled to room temperature after stretching, and the flatness of the present invention can be obtained by controlling the temperature unevenness in the TD direction at this time to 15% or less.

Next, a magnetic layer is provided on this film. In order to provide a metal thin film on the film, it is effective to perform a glow discharge treatment or a corona surface treatment on the surface A in advance to improve the adhesion between the film and the magnetic layer.

Next, a magnetic layer is provided by a method such as vacuum evaporation or sputtering. At this time, curling often occurs with the A side inside, but it is necessary to remove the curl in order to use it as a magnetic recording medium. For this purpose, a method is used in which the film B is heated and shrunk by bringing the surface B into contact with a heating roll or passed through a heating oven.

Further, it is preferable to provide a back coat layer by a known method on the non-magnetic layer surface opposite to the magnetic layer. After these processes are completed, slitting is performed to obtain the magnetic recording medium of the present invention.

[0039]

The present invention will be described in detail below with reference to examples.

The physical properties of the present invention are measured by the following methods.

(1) Tarumi amount The measuring method will be described with reference to FIGS. That is, FIG.
As shown in (1), a film 1 having a width of 610 mm in the TD direction is cut out and prepared for 2 m or more in the MD direction. Transfer the film to two rolls separated by a distance of 2 m.
A load of 0.5 kg / mm ² is applied in the D direction. Pass the thread 2 in parallel with the roll 3 at the center of the two rolls,
The yarn 2 is stretched so as to be in contact with the film 2 and the distance from the yarn 2 to the position of the film farthest from the yarn 2 is measured to determine the amount of tarmi. In addition,
The measurement is performed at 25 ° C. and 50% RH. (2) Coefficient of friction The film is cut into a size of 75 mm x 100 mm, the non-magnetic surfaces are superposed on each other, placed on a flat plate, and the lower film is fixed. On top of this, 200g 60mm x 6
A weight having a square bottom surface of 0 mm is placed, and the upper film is pulled at a speed of 15 cm / min, and the friction coefficient is determined from the tensile tension at that time. In addition, it measured for 48 hours by leaving it to stand in an atmosphere of 23 ° C. and 60% RH, and then adjusting the humidity.

(3) Heat Shrinkage A sample long in the TD direction is cut out so as to have a width of 10 mm and a length of 250 mm, and a mark is drawn at intervals of 200 mm.
After heating this in an oven at 150 ° C. for 10 minutes, the film is taken out and the interval between the marked lines is measured. The shrinkage is determined from the dimensions before and after heating.

(4) Ten-point average roughness Rz Using a thin film level measuring device (ET-10) manufactured by Kosaka Laboratories, stylus tip radius 0.5 μm, stylus load 5 mg, cutoff value 0.008 mm, measurement length The measurement was performed five times under the condition of 0.5 mm, and the average value was expressed.

Example 1 N-methyl-2-pyrrolidone (NMP) was charged into a polymerization vessel, and 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component and 4,4 corresponding to 15 mol% were contained therein. '-Diaminodiphenyl ether was dissolved. Further, 0.08 μm of colloidal silica dispersed in NMP was added to the polymer in an amount of 0.08 μm.
It was added through a 0.6 μm cut filter so as to be 5 wt%. To this was added 2-chloroterephthalic acid chloride corresponding to 99.5 mol% to complete the polymerization.
Further, 97 mol% of the generated hydrogen chloride was neutralized with lithium carbonate, and then ammonia was added in an amount equivalent to 10 mol% to obtain a polymer solution. And polymer concentration 10.7wt%,
The solution viscosity at 30 ° C. was adjusted to 4000 poise to obtain a film forming stock solution (this is referred to as “solution A”).

Next, a solution in which colloidal silica was not added was prepared in the same manner as described above. 0.6 wt%, and the polymer concentration is 10.6 wt%, and 4000 at 30 ° C.
A poise solution was prepared (this is referred to as solution B).

The solution A was cut by 0.7 μm, and the solution B was cut by 1 μm.
After filtration with a m-cut filter, the film was cast from a die onto a metal belt so as to have a final film thickness of 4 μm. At this time, the amount of the stock solution was adjusted so that the layer A was 2.5 μm and the layer B was 1.5 μm. 13 cast film
The solvent was evaporated by heating with hot air at 0 ° C., and the self-holding film was continuously peeled off from the belt. Next, the film was introduced into the water tank, and the residual solvent and the inorganic salts generated by the neutralization were extracted. 1.15 in the vertical direction (MD direction)
It was stretched twice.

Next, the mixture was introduced into a tenter and dried at 300 ° C., stretched, and heat-treated. During this time, the film was stretched 1.4 times in the TD direction. At this time, the temperature unevenness in the TD direction of the stretched portion was 2 ° C. (0.7%). Subsequently, the film was stretched again at 200 ° C. in the TD by 1.035 times, and the tenter outlet was further cooled to room temperature of 25 ° C., but the temperature unevenness was at most 8% throughout the entire cooling process. The portion having the largest unevenness had an unevenness of 2 ° C. at an average temperature of 25 ° C. near the exit of the tenter. The Young's modulus of the obtained film was 1150 kg / mm ^{2 in} the MD direction and 1 in the TD direction.
It was 600 kg / mm ² . Table 1 shows the thickness of the film and the coefficient of friction on the non-magnetic surface side. The moisture absorption was 1.5%.

The obtained film was placed in a vacuum evaporation machine,
After evacuating to 0 ^-5 Torr, Co was run at a speed of 40 m / min along a drum cooled to -10 ° C. to reduce Co to 0.2 μm.
m to a thickness of m. In these steps, there was no problem such as deformation of the film due to heat or wrinkling. This is 2
The film is shrunk by contacting with a heating roll of 00 ° C.
After straightening the curl generated by the vapor deposition, the back coat layer was treated with 0.1%.
5 μm was applied and slit on a magnetic tape, but a tape with excellent flatness was obtained.

Example 2 Using the same polymer solution as in Example 1, a film was formed in the same manner as in Example 1. Tenter temperature is 280 ° C, stretching ratio is M
The D direction was 1.1 times, the TD direction was 1.45 times, and the temperature unevenness was 0.7% at 2 ° C. Re-stretching conditions are the same as in Example 1. The temperature unevenness during cooling was 8%. The properties of this film are shown in Table 1, but the amount of tarmi was small.

Example 1 using the obtained film
A magnetic tape was produced in the same manner as described above, but a good magnetic tape was obtained without any problem such as deformation of the film due to heat or wrinkling in the manufacturing process.

Example 3 Using the same polymer solution as in Example 1, a film was formed in the same manner as in Example 1. Tenter temperature is 300 ° C, stretching ratio is M
D direction is 1.1 times, TD direction is 1.3 times, and temperature unevenness is 5 times.
It was 1.7% at ° C. Re-stretching conditions are the same as in Example 1. The temperature unevenness during cooling was 11%. The properties of this film are shown in Table 1, but the amount of tarmi was larger at both ends than in Examples 1 and 2.

Using this, a magnetic tape was produced in the same manner as in Example 1, but both ends of the film were partially discolored by heat in the process, but there was no problem in the center. There were no problems such as wrinkles when wound up.

Comparative Example 1 A film was formed using the same polymer solution as in Example 1. Tenter temperature is 300 ° C, stretching ratio is 1.1 times in MD direction,
The TD direction was 1.3 times, but the temperature unevenness was 12 ° C and 4 ° C.
There was a large unevenness of%. Re-stretching conditions are the same as in Example 1. On the other hand, the temperature unevenness during cooling was 8%. The properties of the obtained film are shown in Table 1. The film had a large amount of tarmi.

A magnetic tape was produced in the same manner as in Example 1. However, in the process, the portion corresponding to the film thickness was discolored by heat, and wrinkles were formed when the film was run. There were many. A portion having few defects was selected and a magnetic tape having a width of 8 mm and a length of 50 m was used. However, small discoloration and wrinkles were found every few meters, and the evaluation was not acceptable.

Comparative Example 2 A film was formed using the same polymer solution as in Example 1. The tenter temperature is 290 ° C., the stretching ratio is 1.1 times in the MD direction,
The TD direction was 1.3 times and the temperature unevenness was 10 ° C. (3.4%). The temperature unevenness during cooling was 20%. The properties of this film are shown in Table 1, and the amount of tarmi was large.

Using this, a magnetic tape was produced in the same manner as in Example 1, but there was discoloration and wrinkles. The tape had many scratches.

Comparative Example 3 A 3 μm film was formed using the same polymer solution as in Example 1. Tenter temperature is 250 ° C, stretching ratio is M
The D direction was 1.1 times, the TD direction was 1.4 times, and the temperature unevenness was 0.8%. The temperature unevenness during cooling was 17%. Table 1 shows the properties of this film.

An attempt was made to manufacture a magnetic tape in the same manner as in Example 1, but the film was deformed by heat in the process, and could not be manufactured.

[0059]

[Table 1]

[0060]

By using the film of the present invention in which the thickness of the film is specified, a magnetic tape having excellent flatness without wrinkles or thermal deformation at the time of forming the magnetic layer and without scratches can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a method of measuring the amount of tarmi.

FIG. 2 is a diagram illustrating a method for obtaining a tarmi amount.

[Explanation of symbols]

 1: Film 2: Thread 3: Roll

Claims (2)

[Claims] 1. A film of 610 mm width and 2 m length has a thickness of 0.5
A magnetic recording medium characterized in that a magnetic layer is provided on the surface of an aromatic polyamide film having a film thickness of 60 mm or less at the center when a load of kg / mm ² is applied. 2. The magnetic recording medium according to claim 1, wherein the coefficient of friction of the nonmagnetic layer surface is 2 or less.