JPS60237634A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent corrosion resistance, etc. by providing a protective layer having a specific atomic ratio of Si:O by plasma polymn. of a gaseous mixture composed of a gaseous silicon monomer contg. Si, C and H or further N and contg. gaseous O2 on a magnetic layer formed on a substrate. CONSTITUTION:The magnetic layer 10 is formed on the substrate 1 consisting of a polyester film, etc. by using a magnetic paint contg. gamma-Fe2O3 powder, Co-contg. gamma-Fe2O3 powder, Fe-Ni powder, etc. or said layer 10 is formed on the substrate by a vapor deposition method, etc. on a magnetic metal (including an alloy). The gaseous mixture which is composed of the gaseous silicon monomer contg. Si, C and H or further N, such as Si(CH3)4 or hexamethyl disilasane and 5-10vol%, by the volume of said gaseous monomer, a carrier gas such as Ar and is incorporated therein with an extremely slight amt. of gaseous O2 is introduced into a plasma polymerizing device 2 and the plasma-polymerized film 11 consisting of the O-contg. silicon org. compd. having <=0.5 atomic ratio of O:Si is formed as the protective layer on the above-mentioned magnetic layer 10 on the substrate film 1 moving along the peripheral side surface of a cylindrical can 4. The magnetic recording medium A having excellent corrosion resistance and durability is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field and Object] The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with excellent durability and corrosion resistance.

[Background technology]

In general, magnetic recording media are made by binding magnetic powder together with a binder component onto a base film, or by depositing ferromagnetic metals or their alloys on a base film by vacuum deposition, etc. The magnetic layer is easily worn out due to violent sliding contact with the magnetic head, etc. In particular, ferromagnetic metal thin film magnetic recording media formed by vacuum deposition etc. have excellent high-density recording characteristics, but have a large coefficient of friction with the magnetic head. It is susceptible to wear and damage, and it also suffers from gradual oxidation in the air, resulting in deterioration of magnetic properties such as maximum magnetic flux density.

For this reason, various protective film layers have been provided on the magnetic layer to improve durability and corrosion resistance. Forming a plasma-polymerized protective film layer on the magnetic layer [Tetsuo Iijima, Hiroaki Hanabusa, Journal of the Institute of Electronics and Communication Engineers, J67-C, No.
('84)] has been proposed. However, when plasma polymerization is performed using this type of octamethylcyclotetrasiloxane monomer gas, because of its high oxygen content, the monomer gas may react in the gas phase and turn into powder, or octamethylcyclotetrasiloxane decomposes into Si
Due to the formation of an O film, it is not possible to obtain a sufficiently dense and tough plasma-polymerized protective film layer of a silicon-based organic compound, and it is still not possible to sufficiently improve durability and corrosion resistance.

[Summary of the invention]

The present invention was developed as a result of extensive research in view of the current situation, and it was discovered that the magnetic layer is made of silicon atoms, carbon atoms, hydrogen atoms, or a monomer gas of a silicon-based compound consisting of silicon atoms, carbon atoms, and hydrogen atoms, and a monomer gas of a silicon-based compound composed of these atoms and nitrogen atoms, and a volume ratio of the monomer gas to this 7-mer gas. 5-10
Plasma polymerization is performed by exposing to plasma of a mixed gas with vol% oxygen gas, and the atomic ratio to silicon atoms is 0.
．． When a plasma-polymerized protective film layer of a silicon-based organic compound containing 5 times or less of oxygen atoms is formed on a magnetic layer, a sufficiently dense and tough plasma-polymerized protective film layer of a silicon-based organic compound is formed, resulting in improved wear resistance. It has been found that the durability is greatly improved and the corrosion resistance is also sufficiently improved.

In this invention, the plasma polymerization that is performed along with the formation of a plasma polymerized protective film layer on the magnetic layer is performed by silicon atoms,
A very small amount of oxygen gas having a volume ratio of 5 to 10% by volume to this monomer gas is mixed as a carrier gas with a monomer gas of a silicon-based organic compound consisting of carbon atoms and hydrogen atoms, or these and nitrogen atoms, and this mixed gas is ,
It is carried out by plasma polymerization using high frequency,
Since a very small amount of oxygen gas is also used as a carrier gas, as in the case of plasma polymerization using monomer gas of octamethylcyclotetrasiloxane, the monomer gas is It is a dense and tough silicon-based organic material that does not react in the gas phase and turn into powder or form a SiO film, and contains a trace amount of oxygen atoms with an atomic ratio of less than 0.5 times that of silicon atoms. A plasma polymerized protective film layer of the compound is formed, and the durability and corrosion resistance are sufficiently improved. Moreover, the small amount of oxygen atoms contained in the plasma polymerized protective film layer improves the adhesion with the magnetic layer, further improving the durability.

Examples of silicon-based organic compound monomer gas used to form such a silicon-based organic compound plasma polymerized protective film layer include tetramethylsilane, hexamethyldisilazane, vinyltrimethylsilane, trimethylsilylacetylene, etc. Monomer gases of silicon-based organic compounds are preferably used. Radicals are generated from these monomer gases of silicon-based organic compounds by high frequency waves, and the generated radicals react and polymerize to form a film.

In addition, when plasma polymerizing the monomer gas of these silicon-based organic compounds, the oxygen gas mixed and used as a carrier gas has a volume ratio of 5 to 10% by volume relative to the monomer gas of these silicon-based organic compounds. It is preferable to use the mixture within the range of . If the amount of oxygen gas used is too small, the adhesion to the magnetic layer will not be sufficiently improved, and if it is too large, the monomer gas of the silicon-based organic compound will be released in the gas phase. It may react and turn into powder, or silicon-based organic compounds may decompose and produce S.
An iO film is formed, and a dense and tough plasma polymerized protective film layer of a silicon-based organic compound cannot be obtained. In this way, when oxygen gas is mixed in a volume ratio of 5 to 10% with respect to the monomer gas of a silicon-based organic compound, and plasma polymerization is performed using this, the atomic ratio with respect to silicon atoms is A plasma-polymerized protective film layer of a dense and tough silicon-based organic compound containing a trace amount of oxygen atoms of 0.5 times or less is formed. Adhesion is also improved, and wear resistance and corrosion resistance are further improved.

When performing plasma polymerization, the gas pressure and high frequency output of the mixed gas of the silicon-based organic compound 7-mer gas and oxygen gas are such that the higher the gas pressure, the faster the deposition speed, but on the other hand, the higher the gas pressure, the higher the deposition rate. However, if the gas pressure is lowered and the high frequency output is increased, the deposition speed will be slower, but a relatively hard protective film layer made of polymer will be obtained. If the high frequency output is made too high with a low value, the monomer gas will turn into powder and a plasma polymerized protective film layer will not be formed. It is preferably within the range of 1 to 2.0 W/-, and the gas pressure is 0. It is more preferable that O1 to 0.1 Torr and the high frequency output be within the range of 0.3 to 1.0 W/-.

The film thickness of such a plasma polymerized protective film layer of a silicon-based organic compound deposited by plasma polymerization is 20
It is preferable that the thickness is within the range of ~1,000 people. If the film thickness is too thin, the durability and corrosion resistance effects of this protective film layer will not be fully exhibited, and if it is too thick, the spacing loss will be too large and the electromagnetic conversion characteristics will be affected. have a negative impact on

The magnetic layer formed on the substrate is made of γ-Fe203 powder, F
e3O4 powder, CO-containing r-Fe203 powder, Co-containing Fe3O4 powder, Fe powder, C.

Magnetic powder such as Fe-Ni powder or Fe-Ni powder is coated on a substrate together with a binder component and an organic solvent and dried, or C0% Nis Fe, Go-Ni, Co-CrX
Vacuum deposition of ferromagnetic materials such as Co-P and Co-N1-P,
It is formed by depositing it on a substrate by means such as ion blasting, sputtering, and plating.

Further, the magnetic recording medium includes various types of structures that come into sliding contact with a magnetic head, such as a magnetic tape having a synthetic resin film such as a polyester film as a base, a magnetic disk or a magnetic drum having a disk or drum as a base.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 A polyester film with a thickness of 10 μm was loaded into a vacuum evaporation apparatus, and cobalt was heated and evaporated under a vacuum of 5×10 −5 Torr to form a ferromagnetic metal thin film layer of cobalt with a thickness of 100 μm on the polyester film. did. Then,
Using the plasma processing apparatus shown in FIG.
The film was moved from the original fabric roll 3 along the circumferential side of the cylindrical can 4 at a speed of 1 m/win, and set to be wound onto the winding roll 5. At the same time, monomer gas of tetramethylsilane was introduced from the gas introduction pipe 6 at a flow rate of 200 seconds, and oxygen gas was introduced as a carrier gas at a rate of 15 seconds.
cI11 was introduced, and a high frequency of 13.56 MHz was applied with an output of 100 W through the electrode 7 at a gas pressure of 0.1) to form a plasma polymerized protective film layer. After that, the polyester film 1 is cut into a predetermined width as shown in Fig. 2.
A magnetic tape A was prepared on which a ferromagnetic metal thin film layer 10 and a plasma polymerized protective film layer 11 were sequentially laminated. The thickness of the plasma polymerized protective film layer at this time was 300.

In addition, as a result of examining the ratio of the number of silicon atoms and oxygen atoms in the plasma polymerized protective film layer using an Auger electron spectrometer, it was found that the number of silicon atoms/the number of oxygen atoms is 1.
It was 10.32. In the figure, 8 is an exhaust system for reducing the pressure inside the processing tank l, and 9 is a high frequency power source for applying high frequency to the electrode 7.

Example 2 Magnetic tape A was prepared in the same manner as in Example 1 except that the same amount of hexamethyldisilazane monomer gas was used in place of the tetramethylsilane monomer gas in forming the plasma polymerized protective film layer in Example 1. I made it. The thickness of the plasma polymerized protective film layer at this time was 220.

In addition, as a result of examining the ratio of the number of silicon atoms and oxygen atoms in the plasma polymerized protective film layer using an Auger electron spectrometer, it was found that the number of silicon atoms/the number of oxygen atoms is 1.
It was 10.36.

Example 3 In forming the plasma polymerized protective film layer in Example 1, the amount of oxygen gas introduced was changed from 15 sccm to 10 sccm
Magnetic tape A was produced in the same manner as in Example 1, except that the gas pressure was changed to 1 and the gas pressure was 0.0951-rel. The thickness of the plasma polymerized protective film layer at this time was 300. Further, as a result of examining the ratio of the number of silicon atoms to oxygen atoms in the plasma polymerized protective film layer using an Auger electron spectrometer, the ratio of the number of silicon atoms/the number of oxygen atoms was 110.23.

Example 4 In formation 6 of the plasma polymerized protective film layer in Example 1, the amount of oxygen gas introduced was changed from 15 sec to 20 sec.
except that the gas pressure was changed to 0.105 Torr.
Magnetic tape A was produced in the same manner as in Example 1. The thickness of the plasma polymerized protective film layer at this time was 280 mm.

In addition, as a result of examining the ratio of the number of silicon atoms and oxygen atoms in the plasma polymerized protective film layer using an Auger electron spectrometer, it was found that the number of silicon atoms/the number of oxygen atoms is 1.
It was 10.47.

Example 5 α-Fe magnetic powder 600 parts by weight Esresoku CN (manufactured by Block Chemical Industry Co., Ltd. 80 μ, vinyl chloride-vinyl acetate copolymer) Pandenox T-5250 (large 30 μ, manufactured by Nippon Ink Co., Ltd., urethane elastomer) Coronat Shikuni Nippon Polyurethane 10 (manufactured by N Kogyo Co., Ltd., trifunctional low molecular weight unsocyanate compound) Methyl isobutyl ketone 400 Toluene 400 This composition was mixed and dispersed in a hole mill for 72 hours to prepare a magnetic paint. A magnetic layer was formed by coating and drying the film to a dry thickness of 4 μm. Next, a plasma polymerized protective film layer was formed thereon in the same manner as in Example 1 to produce magnetic tape A.

Comparative Example 1 In the formation of the plasma polymerized protective film layer in Example 1, 200 sccn+ of octamethylcyclotetrasiloxane was used instead of tetramethylsilane, addition of oxygen gas was omitted, and the gas pressure was set to 0.1 Torr. Example 1
I made magnetic tape in the same way. The thickness of the plasma polymerized protective film layer at this time was 300. In addition, as a result of examining the ratio of the number of silicon atoms and oxygen atoms in the plasma polymerized protective film layer using an Auger electron spectrometer,
Number of silicon atoms/number of oxygen atoms is 1/1.1
Met.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that in the formation of the plasma polymerized protective film layer in Example 1, the addition of oxygen gas was omitted and the gas pressure was set to 0.1 Torr. The thickness of the plasma polymerized protective film layer at this time was 300.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 2, except that in the formation of the plasma polymerized protective film layer in Example 2, the addition of oxygen gas was omitted and the gas pressure was set to 0.1 Torr. The thickness of the plasma polymerized protective film layer at this time was 280 mm.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 1 except that the formation of the plasma polymerized protective film layer was omitted.

The magnetic tapes obtained in each Example and each Comparative Example were tested for durability and corrosion resistance. The durability test was carried out by subjecting the obtained magnetic tape to a sliding test with a sapphire needle and measuring the number of times until the plasma polymerized protective film layer was scratched.The corrosion resistance test was carried out by subjecting the obtained magnetic tape to a sliding test at 60°C. 90%RH
The maximum magnetic flux density was measured after being left under these conditions for 7 days, and the rate of deterioration was determined by comparing the maximum magnetic flux density of the magnetic tape before being left as 100%.

The table below shows the results.

〔Effect of the invention〕

As is clear from the above table, the magnetic tapes obtained in the present invention (Examples 1 to 5) have a lower deterioration rate and are more durable than the magnetic tapes obtained in Comparative Examples 1 to 4. This clearly shows that the magnetic recording medium obtained by the present invention has further improved durability and corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a plasma processing apparatus used in forming a plasma polymerized protective film layer, and FIG. 2 is a partially enlarged sectional view of a magnetic tape obtained by the present invention. DESCRIPTION OF SYMBOLS 1... Polyester film (substrate), 10... Ferromagnetic metal thin film layer (magnetic layer), 11... Plasma polymerized protective film layer, A... Magnetic tape (magnetic recording medium) Patent applicant Hitachi Maxell Co., Ltd. - Ni, Weekly Figure 1 Figure 2〉 -=-

Claims (1)

[Claims] 1. A magnetic layer is formed on a substrate, and a plasma polymerized protective film layer of a silicon-based organic compound containing oxygen atoms in an atomic ratio of 0.5 times or less to silicon atoms is provided on the magnetic layer. Characteristic Magnetic Recording Medium 25 A magnetic layer is formed on a substrate, and then this magnetic layer is coated with a monomer gas of a silicon-based organic compound consisting of silicon atoms, carbon atoms, and hydrogen atoms, or these and nitrogen atoms, and this monomer gas. A silicon-based organic compound that is subjected to plasma polymerization by exposing it to a plasma of a mixed gas with oxygen gas at a volume ratio of 5 to 10% by volume, and contains oxygen atoms in an atomic ratio of 0.5 times or less to silicon atoms. A method for manufacturing a magnetic recording medium, comprising forming a plasma-polymerized protective film layer on a magnetic layer.