JPH0610858B2 - Magnetic recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium using a base film that has been subjected to a predetermined plasma treatment in order to improve durability.

Prior art and its problems On a non-magnetic support, γ-Fe ₂ O ₃ , Co-containing γ-Fe
_It has been a long time since a magnetic recording medium having a magnetic layer mainly composed of an oxide magnetic powder such as ₂ O ₃ and a binder has appeared.

Further, recently, in order to further improve the recording density, F
e, Co, Ni, Fe-Co, Co-Ni, Re-Co
-Ni, Fe-Co-B, Fe-Co-Cr-B, Mn
A magnetic recording medium composed of ferromagnetic powder such as -Bi, Mn-Al, Fe-Co-V and a binder, and a magnetic recording medium using a metal vapor-deposited thin film or a sputtered thin film as a magnetic layer have been put into practical use, and have been put into the spotlight. I'm dying.

In these magnetic recording media, particularly in applications of magnetic tapes and magnetic disks, the friction coefficient is small, smooth and predetermined running property is exhibited, wear resistance is excellent, and stable running can be performed for a long time. There is a strong demand for stable reproduction under any environmental conditions, reliable reproduction at all times, and durability.

Conventionally, various base films have been pretreated for the purpose of improving durability.

The pretreatment includes chemical treatment, coating treatment, corona discharge treatment and the like.

The chemical treatment methods include acid and alkali treatments. The most effective chemical treatment method is to oxidize the surface using a chemical solution of a strong acid / strong acid agent such as a chromic acid treatment solution and introduce a carbonyl group or a carboxyl group to etch the surface.

However, the chemical solution treatment method has a drawback that not only the cleaning and drying of the film surface are required, but also a large investment is required for waste liquid treatment. In particular, the chromic acid treatment is becoming less used today because the waste liquid is subject to pollution control.

The film coating method requires interaction between the binder system contained in the undercoat and the magnetic layer.

That is, if the composition of the binder and pigment of the magnetic layer is changed, it is necessary to select the optimum undercoating composition. In the coating method, not only such a soft technique is required, but also coating and drying processes need to be prepared, and the cost of the product is inevitable because the coating raw material is consumed.

Corona discharge treatment is a dry process, so cleaning,
Advantageously, no drying or effluent treatment processes are required.

This corona treatment has been performed for a long time,
It has the effect of improving wettability and printability.

However, the corona treatment has a problem that it cannot satisfy the characteristics of a high-performance magnetic recording medium which will be required more and more in the future.

As another method, there is flame treatment, but it is not applicable to magnetic recording media due to strict requirements for dimensional stability.

From such an actual situation, a plasma treatment for the base film has been proposed.

Since the plasma treatment method is composed of only one step and is a dry process, it has advantages that drying and waste liquid treatment are not required and that raw materials such as a binder are not consumed. Furthermore, the plasma treatment method enables continuous production at high speed,
It can be easily incorporated into the magnetic recording medium manufacturing process and does not impede its productivity.

As a plasma treatment for the base film, for example, Japanese Patent Publication No. 57-42889 discloses a technique in which air, oxygen, nitrogen, hydrogen, helium, argon or the like is used as a treatment gas and a plasma having a radio frequency or a microwave frequency is used. It is disclosed.

Further, Japanese Patent Application Laid-Open No. 58-77030 discloses a technique in which oxygen, argon, helium, neon, or nitrogen is used as a processing gas and plasma processing is performed with a predetermined applied current at a commercial frequency.

By these plasma treatments, the adhesive force with the magnetic layer is improved and the durability is improved.

However, it is still insufficient in terms of adhesive strength and durability.

II OBJECT OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium using a plasma-treated base film, which has markedly improved durability and adhesive strength of a magnetic layer.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the present invention relates to a magnetic recording medium characterized in that a magnetic layer is formed on a plasma-treated base film directly or through an underlayer using an inorganic gas containing N, H and O as a processing gas. is there.

IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

The base film material used in the magnetic recording medium of the present invention is not particularly limited as long as it is a non-magnetic plastic, but polyester such as polyethylene terephthalate is usually used. Further, the shape, size, and thickness are not limited, and may be selected depending on the application.

At least the surface of the base film on which the magnetic layer is formed is subjected to plasma treatment.

In the plasma treatment method, an inorganic gas is used as a treatment gas, and discharge plasma of this gas is brought into contact with the base film to perform plasma treatment on the surface of the base film.

The principle is outlined. When a gas is kept at a low pressure and an electric field is applied, the free electrons, which are present in a small amount in the gas, have a very large molecular distance as compared with the normal pressure, and therefore are subjected to an electric field acceleration to 5-1.
Acquires kinetic energy (electron temperature) of 0 eV.

When the accelerated electrons collide with atoms or molecules, the orbits or molecular orbits are separated, and these are dissociated into electrons, ions, neutral radicals, and other normally unstable chemical species.

The dissociated electrons are again accelerated by the electric field to dissociate another atom or molecule, and the chain action immediately turns the gas into a highly ionized state. And this is called plasma gas.

Since gas molecules have few opportunities to collide with electrons, they do not absorb much energy and are kept at a temperature close to room temperature.

In this way, the system in which the kinetic energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called low-temperature plasma. Here, chemical species are subjected to addition such as polymerization while keeping their original shape relatively. The present invention seeks to plasma-treat the base film by utilizing this situation. Since the low temperature plasma is used, there is no heat effect on the base film.

An example of an apparatus for treating the surface of a base film with plasma is shown in FIG. FIG. 1 shows a plasma processing apparatus using a variable frequency power source.

In FIG. 1, a reaction gas is supplied to a reaction vessel R from a processing gas source 1 or 2 via mass flow controllers 3 and 4, respectively. When different gases are supplied from the gas sources 1 or 2, they are mixed and supplied in the mixer 5.

The processing gas may have a flow rate range of 1 to 250 ml / min.

In the reaction container R, a base film supporting device to be processed is installed, and a feeding roll 9 and a winding roll 10 are shown here for the purpose of processing a film for a magnetic tape.

Various supporting devices can be used depending on the form of the base film for the magnetic recording medium to be processed, and for example, a mount-type rotary supporting device can be used.

Electrodes 7 facing each other with a base film to be processed interposed therebetween,
7'is provided, one electrode 7 is connected to the frequency variable power source 6, and the other electrode 7'is grounded at 8.

Further, a vacuum system for evacuating the inside of the reaction vessel R is provided in the reaction vessel R, and this is equipped with a liquid nitrogen trap 1.
1, an oil rotary pump 12 and a vacuum controller 13 are included. These vacuum systems use 0.01-10 Torr in the reaction vessel.
Keep within the vacuum range.

In the operation, first, the inside of the reaction vessel R is evacuated by an oil rotary pump until it becomes 10 ⁻³ Torr or less, and then the processing gas is supplied in a mixed state into the vessel at a predetermined flow rate. At this time, the vacuum in the reaction vessel is 0.01 to 10
Managed by Torr range.

When the transfer speed of the base film to be processed and the flow rate of the processing gas become stable, the variable frequency power supply is turned on. Thus, the moving base film is plasma-treated.

In such plasma processing, the present invention uses an inorganic gas containing N, H, and O as a processing gas.

These inorganic gases are N ₂ , H ₂ , NH ₃ , O ₂ ,
_{O 3, H 2 O, NO} , N 2 O, and suitably selected from among NOx, etc., such as NO _2, a may be used a mixture.

In this case, the content of N in the inorganic gas is 5 to 80 at%, H
Content is 5 to 80 at%, and O content is 0 to 50 at%. If the content range of the content in the above-mentioned inorganic gas deviates from the above range, the present invention becomes ineffective.

When the above-mentioned inorganic gas contains a gas other than N, H, and O, it may be one or more of Ar, Ne, He, and the like.

Further, the frequency of the power supply is set to 10 KHz to 200 KHz.

When the frequency is lower than 10 KHz or higher than 200 KHz, the durability sharply decreases and the adhesive strength sharply lowers.

The applied current, the processing time, etc. may be set under normal conditions.

The base film that has been subjected to such plasma treatment,
It can be confirmed that the contact angle is decreased, and the surface is modified by FTIR (Fourier transform infrared absorption spectrum) to generate N—H bond.

As described above, various magnetic layers can be formed as the magnetic layer formed on the surface of the base film that has been subjected to the plasma treatment.

For example, a magnetic metal such as iron, cobalt, nickel or an alloy thereof may be deposited by means such as vacuum deposition, ion plating, sputtering and plating.

Further, it may be installed by coating and drying a magnetic paint comprising a magnetic powder, a binder, an organic solvent, and other necessary components.

In this case, as the magnetic powder, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and Co-containing γ-Fe are used.
Any of ₂ O ₃ , Co-containing Fe ₃ O ₄ , Fe and the like may be used. Also, there is no limitation on the binder and the like.

These magnetic layers may be formed directly on the plasma-treated surface of the base film, or may be provided via an underlayer.

The underlayer may be formed of an alloy of aluminum, copper, titanium, chromium or the like by ion plating, vacuum deposition, sputtering or the like.

Alternatively, a resin may be applied. In this case, the resin layer may contain fine particles.

V Specific Action and Effect of the Invention The magnetic recording medium of the present invention is used for various purposes.

According to the present invention, N, H, and O are used, and more preferably, the plasma frequency is controlled within a specific range, so that the contact angle is greatly reduced and durability is critically improved. In particular, the still characteristics are remarkably improved and the durability running property is remarkably improved. Further, the adhesive strength with various magnetic layers provided directly or via the underlayer is also remarkably improved.

VI Specific Examples of the Invention Hereinafter, the present invention will be described in more detail by showing specific examples of the invention.

Example 1 A 10 μm polyethylene terephthalate (PET) base film was subjected to plasma treatment using a mixed gas as shown below as a treatment gas.

The plasma treatment conditions were as shown below.

Processing condition 1 Processing gas: a mixed gas of NH ₃ : Ar = 10: 1.

Gas flow rate: 50 ml / min Vacuum degree: 0.1 Torr power source: 100 KHz Base film running speed: 30 m / min Processing condition 2 Processing gas: NH ₃ Gas flow rate: 100 ml / min Vacuum degree: 0.1 Torr power source: 100 KHz base film Traveling speed: 30 m / min Processing condition 3 Processing gas: NO ₂ : H ₂ = 3: 1 mixed gas.

Gas flow rate: 100 ml / min Vacuum degree: 0.1 Torr Power source: 150 KHz Base film running speed: 30 m / min Processing condition 4 Processing gas: NH ₃ : O ₂ = 5: 1 mixed gas.

Gas flow rate: 50 ml / min Vacuum degree: 0.01 Torr Power source: 50 KHz Base film running speed: 30 m / min Processing condition 5 Under processing condition 1, the power supply was 13.56 MHz. The other conditions were the same as those of the processing condition 1.

Processing condition 6 In processing condition 1, the power supply was set to 500 KHz. The other conditions were the same as those in the processing condition 1.

Treatment condition 7 Corona discharge treatment was performed. The corona discharge treatment was carried out at a film processing speed of 30 m / min and a voltage of 200 V using a corona processor P-500VA manufactured by Pillar Co., Ltd.

Processing condition 8 In processing condition 1, the processing gas was Ar.

Processing condition 9 In processing condition 5, the processing gas was Ar.

Processing condition 10 In processing condition 6, the processing gas was Ar.

Further, a magnetic layer was formed on each of the polyester films thus treated by the method as shown below, and
Various magnetic tapes shown in FIGS.

Magnetic layer 1 Fe-Co metal powder 100 parts abrasive _(Al 2 _{O 3} 3 parts Nitrocellulose 6 parts Epoxy resin (trade name Epikote 1004) 4 parts polyurethane (sound trade name NIPPOLAN 5033) 10 parts Solvent 250 parts The above composition The mixture was dispersed in a mill for 5 hours, 4 parts of isocyanate (Coronate L) was added, and it was applied to 10 μm polyethylene terephthalate which had been subjected to the above-mentioned treatment while being subjected to magnetic orientation treatment.

For each of the obtained samples, the following (a), (b),
The tests (c) and (e) were carried out. The processing conditions and test results are summarized in Table 1.

Magnetic layer 2 Co—Ni (composition Co 95 wt% —Ni 5 wt%) was sputtered to a thickness of 0.1 μm.

For each of the obtained samples, the following (b), (c),
The tests (d) and (e) were carried out. Table 3 summarizes the processing conditions and the test results.

Magnetic layer 3 0.1 μm from an ingot of 80 wt% Co and 20 wt% Ni
Was magnetically evaporated in an oxygen-containing atmosphere.

For each of the obtained samples, the following (b), (c),
The tests (d) and (e) were carried out. Table 2 shows the processing conditions and the test results together.

(A) Adhesive strength (1) Adhesive tape was adhered to the magnetic coating side of the prepared 1/4 inch width tape at a constant pressure, and this adhesive tape was separated at a constant speed in the angular direction of 180 ° for peeling. The force required was measured.

(B) Still time (1) It was measured as the time until the image disappeared when a still image was reproduced on a VTR under the conditions of a temperature of 20 ° C. and a humidity of 60%.

(C) Contact Angle The contact angle was measured by a droplet projection method of water using a contact prism column CA-P type (manufactured by Kyowa Kagaku).

(D) Adhesive strength (2) Cut the prepared tape into 1 cm x 1 cm. As an adhesion test, an epoxy resin is attached to the bottom of an iron square column having a bottom of 1 cm × 1 cm and a length of 5 cm, and a tape is attached. Epoxy resin is attached to the upper surface of the tape, and an iron square pole with a bottom of 1 cm x 1 cm and a length of 5 cm is attached to the epoxy resin. Next, after the epoxy resin has hardened, the upper and lower square pillars are pulled using a Tensilon device, and the peeling location at that time is examined.

The peeling between the magnetic layer and the base film surface was marked with x, the magnetic layer and the base film surface were not peeled, and the case where the epoxy resin adhesive surface was peeled or the base film was broken is indicated by ◯.

(E) Still time (2) As still characteristics that make the difference in contact angle and adhesive strength even clearer, when a still image is played back on a VTR under high temperature and high humidity of 60 ° C and 90% humidity The time until it disappeared was measured.

The results are shown in Tables 1 to 3.

The effects of the present invention are apparent from the results shown in Tables 1 to 3.

In the sample treated by the present invention, N—H bond was confirmed on the surface as a result of FTIR.

[Brief description of drawings]

 FIG. 1 is a schematic diagram of a plasma processing apparatus. 1, 2: Processing gas source 3, 4: Mass flow controller 5: Mixer 6: DC, AC and variable frequency power supply 7, 7 ': Electrode 9, 10: Feeding and winding roll 11: Liquid nitrogen trap 12: Oil Rotary pump

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yoshiko Tsuchiya 1-13-1 Nihonbashi, Chuo-ku, Tokyo, TDK Corporation (56) References JP-A-60-228545 (JP, A)

Claims (2)

[Claims] 1. A magnetic recording medium characterized in that an inorganic gas containing N, H and O is used as a processing gas, and a magnetic layer is formed on a plasma-treated base film directly or through an underlayer. 2. The magnetic recording medium according to claim 1, wherein the plasma treatment is performed at a frequency of 10 KHz to 200 KHz.