JPH02265743A - Base film for magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a substrate film for magnetic recording media. More specifically, the present invention relates to a substrate film for magnetic recording media that is suitable for high-density magnetic recording and has excellent antistatic properties and adhesive properties.

[Prior Art] Biaxially stretched polyester films are conventionally known as substrate films for magnetic recording media.

However, in coated magnetic recording media in which a magnetic recording layer containing magnetic particles and an organic binder is coated on the surface of a two-wheeled stretched polyester film, static electricity generated when the magnetic tape runs or when the magnetic disk rotates causes Due to the adhesion of dust and the like, there have been problems such as dropouts occurring and damage to the magnetic recording medium and magnetic head.

For this reason, it is necessary to impart antistatic properties to coated magnetic recording media, and the following methods are known.

■A method in which fine particles of carbon, metal, etc. are added to the magnetic recording layer to impart conductivity to the magnetic recording layer itself.

■A method of imparting conductivity to a substrate film by adding or coating a surfactant or conductive polymer inside or on the surface of a biaxially stretched polyester film (Japanese Patent Laid-Open No. 57-60
536, USP No. 4617226).

■A method of applying carbon-containing paint to the surface of a biaxially stretched polyester film to impart conductivity to the substrate film (Japanese Patent Laid-Open Nos. 55-55433 and 1982-1115)
.

(2) A method of imparting electrical conductivity to a substrate film by applying a paint containing fine metal oxide particles to the surface of a biaxially stretched polyester film (Japanese Patent Laid-Open No. 62-89219).

■0.1 μm to 1 on the surface of two-wheel stretched polyester film
A method of imparting conductivity to a substrate film by laminating metal films of about μm size (Japanese Unexamined Patent Publication No. 1115-1983).

■A method of applying an island-like and/or mesh-like conductive layer made of a non-magnetic metal to the surface of a biaxially stretched polyester film previously proposed by the present inventors (Japanese Patent Application No. 63-9397
3).

[Problems to be Solved by the Invention] However, such conventional antistatic methods have the following problems.

In method (2), in order to provide sufficient antistatic properties, it is necessary to add a large amount of conductive fine particles, which may result in a decrease in output or damage to the surface properties due to the added particles, resulting in dropouts. occurs.

In method (2), the surfactant does not exhibit sufficient conductivity in a low-humidity environment, resulting in insufficient prevention of static electricity, resulting in dust adhesion and dropouts.

In method (2), in order to provide sufficient antistatic properties, it is necessary to apply a large amount of paint containing fine carbon particles, and as a result, the surface properties may be impaired due to secondary agglomeration of the fine carbon particles. , the adhesion with the magnetic recording layer is impaired.

Similarly to method (2), since a paint containing a large amount of metal oxide fine particles is applied, the surface properties are impaired due to secondary aggregation of the fine particles, and the adhesion to the magnetic recording layer is impaired.

In method (2), the adhesion between the metal film and the substrate film and the adhesion between the metal film and the magnetic recording layer are insufficient, and the flexibility for bending etc. is poor, so when running as a magnetic tape, There was a problem in that the magnetic recording layer would come off when it was rotated as a floppy disk.

As a method to solve the problems of ■～■, the present inventors
The above method (■) was proposed, and (■) is a substrate film for magnetic recording media that has excellent antistatic properties and excellent surface properties and adhesive properties. There was a problem with this, and the laminated conductive layer had the disadvantage of causing scratches when running.

The present invention was devised in view of the drawbacks of the prior art, and its purpose is to provide excellent adhesion to the magnetic recording layer, improve runnability when coating the magnetic recording layer, and provide excellent antistatic properties. An object of the present invention is to provide a substrate film for a magnetic recording medium.

[Means for Solving the Problems] That is, the present invention has a conductive layer laminated on at least one surface of a biaxially stretched polyester film, and a magnetic recording layer containing magnetic particles and an organic binder on the conductive layer. In a substrate film for a magnetic recording medium comprising a laminated layer of
The present invention provides a substrate film for a magnetic recording medium, characterized in that the conductive layer is made of a nonmagnetic alloy containing at least one of iron, cobalt, and nickel, or palladium, and contains fluorine.

FIG. 1 shows an example of the substrate film for a magnetic recording medium of the present invention, in which a conductive layer 2 and a magnetic recording layer 3 are formed in this order on one side of a biaxially stretched polyester film 1. FIG. 2 shows another example of the substrate film for magnetic recording media of the present invention, in which a conductive layer 5 and a magnetic recording layer 6 are formed on both sides of a two-wheel stretched polyester film 4.
are formed in this order.

The biaxially stretched polyester film in the present invention is
Known polyesters, for example, at least one difunctional carboxylic acid such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, bis-α, β(2-chlorophenoxy)ethane-4,4′-dicarboxylic acid, adipic acid, sebacic acid, etc. A polyester obtained by condensation polymerization of a seed and at least one glycol such as ethylene glycol, triethylene glycol, tetramethylene glycol, and hexamethylene glycol is melt-extruded into a sheet or tube shape, and then simultaneously or Stretched in two directions, vertically and horizontally, by sequential biaxial stretching. The step of stretching in one direction may be divided into two or more times, or the stretching may be repeated in a length-to-width direction, a width-to-length direction, and the like.

Furthermore, the biaxially stretched polyester film may be a copolymer of polyester and other polymers, or a mixture of polyester and other polymers, as long as the object of the present invention is not impaired. .

Additionally, known additives such as plasticizers, lubricants, colorants, etc. may be added to the biaxially stretched polyester film.

In addition, prior to laminating the conductive layer, the biaxially stretched polyester film is subjected to surface treatments such as corona discharge treatment, plasma treatment, glow discharge treatment, reverse sputter treatment, and surface roughening treatment.
A known anchor coat treatment may be applied.

The thickness of the plastic film of the present invention is not particularly limited, but from the viewpoint of suitability as a magnetic recording medium, the thickness is 3 μm to 20 μm.
A range of 0 μm is desirable. In terms of mechanical properties and flexibility, the thickness is more preferably in the range of 5 μm to 100 μm.

The surface roughness of the biaxially stretched polyester film of the present invention is
Although not particularly limited, the average surface roughness (Ra) is 0.00
2 to 0.05 μm, maximum surface roughness (Rt) is 0.00
The thickness is preferably in the range of 5 to 0.2 μm.

A conductive layer is laminated on at least one surface of the biaxially stretched polyester film, and in the present invention, the conductive layer is made of at least one of Fe, Co, and Ni such as SUS, Ni-Cr, and Hastelloy. Non-magnetic alloys containing palladium, etc. can be used, and are important in terms of long-term stability of adhesive strength and conductivity with the biaxially stretched polyester film and the magnetic recording layer. Furthermore, it is important that the conductive layer contains fluorine in order to improve running properties when applying the magnetic recording layer. In order to improve the runnability when applying the magnetic recording layer and not to impair the adhesive force with the magnetic recording layer, the proportion of the fluorine atoms in the conductive layer should be adjusted to the total amount of metal atoms. , preferably in the range of 0°01 to 0.3.

The thickness of the conductive layer is such that the average amount of adhesion per side is 0.
It is desirable that the range is from 0.005g/rrf to 0.05g/nf.If it is less than 0.005g/nf, sufficient antistatic function will not be exhibited, and if it exceeds 0.05g/d, the adhesive strength and surface properties will deteriorate. This is not preferable because flexibility is impaired. More preferably, 0°008g/rrf to 0.02g/rrf
It is desirable that it be in the range of rrr. In order for the conductive layer to exhibit both sufficient adhesion with the substrate and with the magnetic recording layer, the conductive layer itself must be formed in an island or mesh shape, that is, conductive. Rather than the layer covering the entire surface of the substrate, it is desirable that the conductive layer be formed on a portion of the substrate and not formed on other portions. The adhesive force between a metal and a polymer is weak because Van der Waals force is dominant, and when a conductive layer is formed on the entire surface of the substrate, the adhesive force actually decreases.

The surface electrical resistance of the conductive layer is preferably 1010 ohms/□ or less in order to exhibit good antistatic properties, and when the magnetic recording medium is used, the user's body is not electrically charged. In order to prevent electric charges from discharging through the magnetic recording medium to the chassis etc. and destroying the recording, 10.
It is preferable that it is 2 ohms/□ or more. More preferably, it is in the range of 104 to 109 ohms/□.

As a method for forming a conductive layer on the surface of a biaxially stretched polyester film, methods such as vacuum evaporation, sputtering, and ion blating, which are performed by introducing a fluorine-containing gas into a vacuum, can be employed.

Among these, sputtering is most preferred in order to maximize the effects of the present invention.

Sputtering in the present invention refers to direct current two-pole sputtering,
All known sputtering methods are included, such as high frequency bipolar sputtering, DC magnetron sputtering and high frequency magnetron sputtering.

When performing such sputtering, it is necessary to introduce a gas containing fluorine into the vacuum at the same time as an inert gas such as argon. As the gas containing fluorine, perfluoroalkanes such as tetrafluoromethane, hexafluoroethane and octafluoropropane, and fluoroalkanes such as difluoromethane, trifluoromethane and difluoroethane can be used. Among these, perfluoroalkanes such as tetrafluoromethane and hexafluoroethanato are preferred.

To form a conductive layer in the form of islands or networks, methods include controlling the amount of deposition during vacuum deposition or sputtering, keeping the temperature of the biaxially stretched polyester film substrate high, and introducing a small amount of inert gas. is effective, but other pretreatments include strong glow discharge treatment of the substrate, plasma treatment, plasma polymerization of fluorine-based resin, corona discharge treatment after forming a conductive layer, and plasma treatment. It can also be formed into an island shape or a mesh shape by post-processing such as .There is no particular limitation.

After forming the conductive layer, a magnetic recording layer containing magnetic particles and an organic binder is formed on the conductive layer.

Examples of magnetic particles include, but are not limited to, iron oxide represented by γ-hematite, cobalt-added iron oxide, chromium oxide, barium ferrite, iron fine particles, and the like.

As the organic binder, urethane resin, epoxy resin, vinyl chloride, vinyl chloride-vinyl acetate copolymer, phenoxy resin, polyester resin, etc. can be used.

In addition, known additives such as aluminum oxide, carbon black, lubricants such as stearic acid and amyl stearate, antiwear agents, and dispersants may be included.

[Applications] The substrate film for magnetic recording media obtained by the present invention has excellent surface properties and adhesion with the magnetic recording layer, so it can be used for high-density magnetic materials such as magnetic tapes such as video tapes, floppy disks, video floppy disks, etc. It can be widely used for recording media.

[Effects of the Invention] Since the substrate film for magnetic recording media of the present invention has the above-mentioned structure, it not only has excellent adhesive properties, but also has excellent antistatic properties when applying a magnetic recording layer, and has good adhesion properties when applied to a conductive layer. There is no risk of scratches occurring, thus increasing yield. In addition, when used as a high-density magnetic recording medium, the humidity ranges from low to high humidity.
Since it exhibits stable conductivity in a wide range of usage environments from low to high temperatures, it runs and rotates stably, and there are fewer dropouts due to dust adhesion.

Examples will be described below.

The following method was used to measure the characteristics in the present invention.

(1) Surface electrical resistance Apply conductive paste to both ends of the sample (width 30 mm x length 35 mm) in the longitudinal direction so that the electrode spacing is 30 mm to form electrodes. (manufactured by Ray Co., Ltd.).

The current value was measured at an applied voltage of 1 to 1000 V, and the surface electrical resistance was calculated.

(2) A polyester adhesive tape Na31B (manufactured by Nitto Denko Corporation) is strongly adhered to the surface of the film laminated with the adhesive conductive layer and the magnetic layer, and peeled off in a 180 degree direction. When the conductive layer or magnetic layer did not peel off at all, the evaluation was 0; when the conductive layer or the magnetic layer was peeled off a little, the evaluation was △; when the entire surface peeled off, the evaluation was rated ×.

(3) Antistatic electrostatic copying paper tester (SP428) manufactured by Kawaguchi Electric Co., Ltd.
A DC voltage of 5 kV was applied to the sample surface for 5 seconds, the voltage application was stopped, and the surface potential was measured 1 second later.

(4) Amount of adhesion Measured by atomic absorption spectrometry.

(5) Measuring method of friction coefficient of substrate film ASTM (^
merican 5standard Te5t Met
hod) - The friction coefficient was measured by the method described in D1894-78. In Table 1 in Examples and Comparative Examples, the static friction coefficient and the dynamic friction coefficient are expressed as μ, μ, respectively.

Examples 1 to 3, Comparative Examples 1 to 3 A palladium film was formed on a biaxially stretched polyethylene terephthalate film ("Lumirror" manufactured by Toshishiki Co., Ltd.) as a substrate using a magnetron sputtering device.

Sputtering was carried out using a palladium plate (purity 99.9%, size 5 inches x 12 inches) at 5X.
After evacuation to 10-5 Torr, argon gas was
25 l/min, C2F6 gas 0, 02
The experiment was carried out under the conditions that the power was introduced at 1/min and the input power was 0.6 KW (7).

The amount of deposited palladium film containing fluorine was determined by adjusting the sputtering time.

Adhesion amount is 0. O1g/rrr, 0.015g/i, 0.
02g/rrr respectively as Example 1.2.3.

The gas introduced into the vacuum chamber is argon gas only, and the amount introduced is 0. 25 Example 1~ except that the speed was set at 1/min.
Comparative Examples 1.2.3 were carried out in the same manner as in 3, and the amounts of palladium film deposited were set to 0°01 g/a, 0.015 g/po, and 0.02 g/a, respectively.

These Examples 1 to 3. On the palladium films of Comparative Examples 1 to 3, a magnetic paint (magnetic paint "Daifera Coat" VD-1653, manufactured by Dainichiseika Chemical Co., Ltd.) was applied and dried to a dry thickness of 4 μm.

Examples 1-3. Table 1 shows the measurement results of the adhesion amount 1 surface electrical resistance, antistatic property, coefficient of friction, and adhesion of the magnetic layer laminate films of Comparative Examples 1 to 3. Further, the ratio of fluorine atoms to palladium atoms in the conductive layers of Examples 1 to 3 was 0.08. The surface roughness of the biaxially stretched polyethylene terephthalate film used as the substrate was Ra=6 nm and Rt=70 nm.

Comparative Example 4 Magnetic paint A was applied and dried in the same manner as in Example 1, but without providing a conductive layer, on the biaxially stretched polyethylene terephthalate film used in Examples 1 to 3.

Table 1 shows the measurement results of the surface electrical resistance, antistatic property, coefficient of friction, and adhesion of the film obtained by laminating a magnetic layer on Comparative Example 4 of the sample of Comparative Example 4.

Example 4. 5. 6 Using a nickel-chromium alloy (weight ratio, nickel nichrome = 80:20) as a sputtering target, the amount of argon gas introduced was 0.18/ml, and the amount of SCF4 gas introduced was 0.18/ml. A conductive layer laminate film and a magnetic layer laminate film were produced in the same manner as in Example 1 except that 03 I/win was used.

The amount of nickel-chromium alloy film deposited was determined by adjusting the sputtering time.

Adhesion amount is 0.01g/resistant, 0.02g/I, 0゜04g
/m are respectively referred to as Example 4.5.6. The ratio of fluorine atoms to the total amount of nickel and chromium metal atoms in the conductive layers of Examples 4 to 6 was 0.10. Adhesion amount 9 Surface electrical resistance of conductive layer laminated films of Examples 4 to 6,
Table 1 shows the measurement results of the antistatic property, friction coefficient, and adhesiveness of the magnetic layer laminate film.

Example 7. 8. 9 Stainless steel plate (SUS304, thickness 5rnm, size 5 inches x 12
inch), and the amount of argon gas introduced is 0.30
I/mi3 The amount of C2F6 gas introduced is 0, 03 1/
A conductive layer laminate film and a magnetic layer laminate film were produced in the same manner as in Example 1, except that win was selected.

The amount of the 5US304 alloy film deposited was determined by adjusting the sputtering time.

The adhesion amount is 0.01g/i, 0. 02g/rrf, 0
Example 7. 8.
9. The ratio of fluorine atoms to the total amount of iron, chromium, and nickel metal atoms in the conductive layers of Examples 7 to 9 was 0.1.
It was 2.

Adhesion amount of conductive layer laminate films of Examples 7 to 9.

Table 1 shows the measurement results of surface electrical resistance, antistatic property, coefficient of friction, and adhesion of the magnetic column layer laminated film.

Comparative Example 5 A palladium film was formed on a biaxially stretched polyethylene terephthalate film in the same manner as in Comparative Example 1, except that the amount of deposition was changed. The sputtering time was adjusted so that the amount of adhesion was 0.10 g/rr'r. A magnetic material was applied onto this palladium film in the same manner as in Examples 1 to 3 and dried. Table 1 shows the measurement results of the adhesion amount 1 surface electrical resistance, antistatic property, coefficient of friction, and adhesion of the magnetic layer laminate film of the sample of Comparative Example 5.

Table 1 shows the measurement results for each sample of Examples 1 to 9 and Comparative Examples 1 to 5.
However, as is clear from Table 1, Examples 1 to 1 of the present invention
No. 9 had excellent antistatic properties, a small coefficient of friction, and excellent adhesion to the magnetic recording layer. On the other hand, Comparative Example 1. 2. 3. Comparative Example 5 had a large coefficient of friction and could cause scratches during running when applying the magnetic recording layer, and Comparative Example 5 had poor adhesion to the magnetic recording layer.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are schematic cross-sectional views each showing an example of a substrate film for a magnetic recording medium of the present invention. 1.4: Biaxially stretched polyester film, 2.5:
Conductive layer, 3, 6: magnetic recording layer

Claims (1)

[Claims] 1. A magnetic recording comprising a conductive layer laminated on at least one surface of a biaxially stretched polyester film, and a magnetic recording layer containing magnetic particles and an organic binder laminated on the conductive layer. In the media substrate film, the conductive layer is made of iron,
1. A substrate film for a magnetic recording medium, comprising a nonmagnetic alloy containing at least one of cobalt and nickel, or palladium, and containing fluorine. 2 Average adhesion amount per side of conductive layer is 0.005g/
m^2 to 0.05 g/m^2, formed in an island or mesh shape, and has a surface electrical resistance in the range of 10^2 ohm/□ to 10^1^0 ohm/□. The substrate film for magnetic recording media according to claim 1, characterized in that: