JPH027221A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesive property of a magnetic layer and base film and to adjust electric charge by providing a primer layer contg. a charge transfer type boron polymer on the surface of a polyester film and further, providing the magnetic layer thereon. CONSTITUTION:A linear satd. polyester resin synthesized from arom. dibasic acid or the ester formable deriv. thereof and diol or the ester formable deriv. thereof is melt-extruded to form the polyester film. The primer layer contg. the charge transfer type boron polymer is coated on one or both surfaces of the polyester film and the magnetic layer is provided on this layer. The adhesiveness between the magnetic layer and the base film is enhanced in this way and the charge thereof is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium in which a base film and a magnetic layer are firmly adhered to each other, and the charge of the medium is adjusted.

<Prior Art> It is known to melt-extrude thermoplastic polyesters, such as polyethylene terephthalate or its copolymers, polyethylene naphthalate or its copolymers, or blends of these with small proportions of other resins, to form films. be. It is also known that the resulting biaxially stretched and heat-set polyester film has superior mechanical properties, heat resistance, gas barrier properties, electrical properties, and chemical resistance compared to films made of other resins. However, because its surface is highly crystalline oriented, its surface cohesion is high, making it suitable for paints, adhesives, inks, and magnetic coatings.

Poor receptivity to vapor-deposited alloys, etc.

Therefore, when a magnetic paint layer or a vapor-deposited alloy layer is provided on the surface of such a polyester film, the surface of the film is subjected to corona treatment, ultraviolet irradiation treatment, plasma treatment, or flame treatment to strengthen the adhesion between the two. It is known to apply the above-mentioned layer after activating the .

However, although these methods of activating the film surface can be expected to improve adhesion to the coating layer by increasing the secondary bonding force due to wetting, the activity decreases over time. Therefore, these means of activating the film surface are not necessarily satisfactory.

As another method for increasing the receptivity of the polyester film surface, an etching method has been proposed in which the surface is swollen or partially dissolved with various agents.

This method coats the film surface with an acid, alkali, or amine aqueous solution.
! ~The surface of the film is etched by contacting with chemicals such as lychloroacetic acid or phenols, and the crystal orientation near the surface is decomposed, dissolved, and relaxed, and at the same time, the cohesiveness is reduced and the adhesion with the binder resin is increased. The effect is the most reliable, and the adhesion between the film and the layer provided thereon, such as the magnetic layer, is strong.

However, some of the chemicals used in this method are harmful and can be dangerous to handle, and volatile substances from the chemicals are released into the atmosphere. There are various disadvantages in practical terms, such as the need for caution.

As a method similar to this method, there is a method in which a primer layer (undercoat layer) is previously provided on the surface of the film, a thin surface layer that is different from Bethfilm is formed, and then a desired layer is formed. From polyurethane to polyester.

Many polymers such as acrylic resin and polyether have been proposed. However, as the recording density of magnetic recording media increases and the surface of the base film becomes flat, blocking of the primer-treated film may occur, the adhesion with the magnetic layer may become unstable, and in some cases, the primer may cause the film surface to become flat. often inhibits. Since the thickness of the primer layer must be increased in order to improve adhesion, unevenness in the thickness of the primer layer is likely to occur.

On the other hand, charge adjustment is important in magnetic recording media. When the magnetic layer becomes thicker, the surface resistance of the base film must be lowered, and dust adhesion and roll separation due to frictional electrification of the base film during application of the magnetic layer also pose practical problems. Conventionally, a method of mixing antistatic agents into the primer layer has been adopted as a countermeasure against these problems, but these antistatic agents are highly dependent on humidity, tend to cause blocking, and have a strong tendency to reduce adhesive strength. Ta. In particular, it was difficult to provide both adhesiveness and charge adjustment function.

<Object of the Invention> An object of the present invention is to provide a magnetic recording medium based on a polyester film, which has improved adhesion between the magnetic layer and the base film, and has controlled charge. .

<Configuration/Effects of the Invention> According to the present invention, a magnetic film is produced by providing a primer layer containing a charge-transfer type poron polymer on at least one side of a polyester film, and further providing a magnetic layer thereon. Achieved by recording media.

In the present invention, polyester is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate,
Polyethylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate), polyethylene-
Examples include 2゜6-naphthalene dicarboxylate,
Copolymers of these or blends of these with small proportions of other resins are also included.

A polyester film can be obtained by melt-extruding such a linear saturated polyester resin, forming it into a film by a conventional method, and subjecting it to orientation crystallization and heat treatment crystallization. This polyester film is preferably crystal oriented to such an extent that the heat of crystal fusion measured by a scanning calorimeter in a nitrogen stream [at a heating rate of 10° C./min] is usually 4 Cal/g or more.

The charge transfer type boron polymer in the present invention is B or N
It consists of a regular repeating structure of -8 complexes. Two examples are shown schematically as follows (Plastic Niji, February issue No. 87, p. 147, Fig. 2).

The charge transfer type boron polymer can also be used as a composite with an organic amorphous semiconductor.

This composite can be obtained, for example, by clathrating an organic amorphous semiconductor in a solution of a charge-transfer type boron polymer matrix.

In the present invention, the primer layer containing the charge-transfer type boron polymer can be formed by applying a primer liquid containing the charge-transfer type boron polymer to one or both sides of a polyester film and drying the primer layer. This primer liquid may be an aqueous solution, an aqueous dispersion, or an organic solvent solution.
In addition to the charge transfer type boron polymer, the primer solution contains binders such as polyurethane, polyester, and acrylic resins, fine particles such as silicon oxide, titanium oxide, and crosslinked acrylic, lubricants, surfactants, stabilizers, etc. A curing agent, a catalyst, an antistatic agent, a dispersant, etc. can be added. The ratio of the charge transfer type boron polymer (or its complex) in the solid content of the primer is 0.5 to 100.
It is preferably 5% to 100% by weight.

Although the solid content concentration in the primer solution can be freely selected,
It is preferably 0.1 to 40% by weight.

The primer solution is usually applied to the polyester film before or after crystal orientation is completed. A polyester film before crystal orientation is completed is an unstretched film obtained by melting a polymer and making it into a film as it is;
A uniaxially stretched film in which an unstretched film is oriented in either the vertical direction or the horizontal direction;
This includes a biaxially stretched film (before it is finally re-stretched in the vertical or horizontal direction to complete oriented crystallization). Among these, it is preferable to apply it to a -axially stretched film from the viewpoint of economy and cleanliness. In other words, the quality is high because the primer is applied during the polyester film manufacturing process.

This is advantageous in terms of cost.

The final dry film thickness of the primer layer is 10 to 2
It is preferably μm, but can be freely selected. The coating is preferably performed by a roll coating method, a gravure coating method, or the like.

In the present invention, a magnetic layer is provided on the primer layer. Examples of the magnetic layer include those conventionally used or known as magnetic layers for video tapes, audio tapes, floppy disks, and the like. For example, by applying a magnetic paint in which ferromagnetic powder such as iron oxide, V-based chromium, barium ferrite, etc. is dispersed in a binder such as polyurethane, vinyl acetate-vinyl chloride copolymer, 21-cellulose, etc. can get. In addition to the magnetic paint, a ferromagnetic film can be obtained by forming an alloy containing metals such as Fe and Co by means such as vapor deposition or sputtering.

The magnetic layer can have various thicknesses depending on the use and purpose, but
．． The thickness is preferably 0.05 to 5 μm.

In the magnetic recording medium of the present invention, since the adhesion between the magnetic layer and the base film is extremely improved by the primer layer, a decrease in yield due to powder falling off of the magnetic layer can be avoided. This also means that the degree of freedom in designing the magnetic layer increases. In particular, interfacial adhesion tends to decrease due to miniaturization of magnetic powder and increase in filling ratio, so this can be prevented.

Furthermore, magnetic recording media have the characteristic that their charge is controlled. That is, as a base film with a primer, the surface resistance is reduced, and the surface resistance of the magnetic layer surface is also adjusted to be reduced. Further, even if the surface resistance of the primer layer is not so low, a non-electrification diffusion effect can be produced due to the tunnel effect. The charge adjustment effect also acts through the film layer, so even if a charge-transfer type boron polymer-containing primer layer is provided on only one side of the Bessfilm, the charge on the opposite non-magnetic surface will rapidly attenuate, and the magnetic recording medium will The running performance and handling properties are improved. Furthermore, the non-electrification prevents errors due to adhesion of dust and the like and eliminates noise, making it extremely effective in magnetic recording.

<Example> The present invention will be further explained below with reference to Examples.

Note that "parts" in the examples mean "parts by weight." Moreover, each characteristic of the film was measured by the following method.

1. Coating the following magnetic paint on the magnetic base film under the specified conditions, and applying Scotch tape No.

600 (3M company! Width 19.4 m/m, length 8 cm) was pasted without air bubbles, and then JIS-C27
The sample was smoothed using a manual load roll described in 01 (75), and the sample was peeled in a T-shape using a Toyo Seiki Co., Ltd. Tensilon at a head speed of 300 mm/min to measure the peel strength. Find g/c by dividing this by the tape width.
Find it as m.

Note that in T-peeling, the laminate was placed with the tape side facing down, and the distance between the tension chucks was 5 cm.

[Preparation of magnetic paint for evaluation] Nitrocellulose R31/2 as lacquer thinner for paint
[Freus containing 25% isopropanol.

Daicel ■] was dissolved to prepare 40 parts 1% solution, and 43.8 parts of this solution was added, followed by 32.5 parts of polyester resin (Desujofen 1 F00. manufactured by Bayer AG) and 200 parts of chromium dioxide powder. Part 1 Soybean oil fatty acid (Legion P, manufactured by Riken Vitamin ■) as a dispersant/wetting agent.

Cationic activator (Cation 8 B2 NOF (manufactured by 11)
and 1 part and 0.5 part of squalene (shark liver oil), respectively.

Add 0.8 parts to a ball mill. Methyl ethyl ketone (
MEK (abbreviated below)/cyclohexanone/toluene = 3
282 parts of a mixed solvent consisting of /4/3 (weight ratio) was further mixed and sufficiently pulverized to form a mother liquor paint (45 wt%
). To 50 parts of this mother liquor, 48 parts of trimethylolpropane and toluylene diisocyanate addition reaction product
1 part (Coronet 1 to L 2 manufactured by Nippon Polyurethane Industries) was added with 6.25 parts of butyl acetate to give a final weight of 42.75 wt.
% of magnetic paint for evaluation is obtained.

The paint described above is dried on a base film at 80° C. for 1 minute, further aged at 60° C. for 24 hours, and then roll-coated to a predetermined coating thickness. Measure the adhesion of the magnetic paint on the medium being coated.

2. Surface resistivity Primer, set the resistivity value of the magnetic paint coated surface to 20'C,
Measured under the condition of 50% RH.

Example 1 Polyethylene terephthalate (containing calcium carbonate as a lubricant) with an intrinsic viscosity of 0.65 measured in 0-chlorophenol at 25°C was melt-extruded onto a rotating cooling drum maintained at 20°C to produce an unstretched film with a thickness of 197 μm. Then, after stretching the unstretched film 3.6 times in the machine axis direction, a charge transfer type boron polymer [Hyboron N5CA
A 2% aqueous solution of J (manufactured by fiJ Boron International) was coated on one side of a uniaxially stretched film using a kiss coat method using a 4 (1/wet) matrix.Subsequently, it was stretched 3.9 times in the transverse direction at 105°C. and further heat treated at 205℃,
A biaxially oriented polyester film coated with a primer on one side and having a thickness of 14 μm was obtained.

Next, apply the magnetic paint described above to the primer surface and dry it (
The thickness of the magnetic layer was 5 .mu.m) to prepare a magnetic recording medium. This characteristic is shown in Table-1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the primer was not applied. The properties of the obtained magnetic recording medium are shown in Table 1. Example 2 A charge transfer type boron polymer was coated on one side of a biaxially stretched film (thickness 20 μm) of polyethylene terephthalate containing a lubricant (calcium carbonate) using a gravure coating method. [A 2% solution of Hiboron CTN-131J (■ Boron International) was applied and dried to form a primer layer with a thickness of 0.1 μm.

Next, the above-mentioned magnetic paint was applied to the primer surface and dried (magnetic layer thickness: 5 μm). Table 1 shows the characteristics of the obtained magnetic recording medium.

Example 3 In Example 1, [Hyboron N5
The procedure was carried out in the same manner as in Example 1, except that instead of the CAJ aqueous solution, a 2% aqueous solution of a mixture (solid content ratio 50150) of Hiboron N5CAJ and polyurethane emulsion "Merci 545" (Toyo Polymer (! Wooden)) was used. Table 1 shows the characteristics of the obtained magnetic recording medium.

Example 4 Intrinsic viscosity measured in O-chlorophenol at 25°C 0
．． 64 polyethylene terephthalate (containing lubricant) 2
Melt extruded onto a rotating cooling drum maintained at 0°C to a thickness of 1
．． After stretching the unstretched film by 3.6 times in the machine axis direction, the uniaxially stretched film was coated with a 2% aqueous solution of Hiboron N5CAJ at 2 g/m (wet) using a kiss coating method. It was coated on both sides.Subsequently, it was stretched 3°9 times in the transverse direction at 105°C, and further stretched at 210°C.
The film was heat-set at .degree. C. to obtain a biaxially oriented polyester film coated with primer on both sides and having a thickness of 75 .mu.m.

Next, the magnetic paint described above was applied to both primer surfaces and dried (magnetic layer thickness: 0.8 μm). Table 1 shows the characteristics of the obtained magnetic recording medium.

Table Example 5 A Co--Ni alloy was deposited to a thickness of 0.1 μm on the primer-coated surface of the primer-coated film obtained in Example 1.

Table 2 shows the surface resistivity of the obtained magnetic recording medium.

Comparative Example 2 Table 2 shows the characteristics when vapor deposition was performed in the same manner as in Example 5 on a film to which no primer was applied. This magnetic recording medium had a lower adhesion force between the deposited film and the film than that of Example 5.

table

Claims (1)

[Claims] A magnetic recording medium comprising a primer layer containing a charge-transfer type boron polymer provided on at least one side of a polyester film, and further provided with a magnetic layer thereon.