JPS6057537A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability and corrosion resistance by exposing a magnetic layer into the plasma of a gaseous mixture composed of the gaseous monomers of silicon atom, carbon atom, hydrogen atom or said atoms and specific two kinds of org. silicon compds. to form a protective film layer. CONSTITUTION:A magnetic layer is exposed into the plasma of a gaseous mixture composed of the 1st gaseous monomer of an org. silicon compd. consisting of silicon atom, carbon atom, hydrogen atom or said atoms and nitrogen atom and the 2nd gaseous monomer of an org. silicon compd. contg. silicon atom and oxygen atom and having an unsatd. bond to perform plasma polymn. in the case of forming the protective film layer. The 1st gaseous monomer is preferably, for example, tetramethylsilane, etc. and the 2nd gaseous monomer is preferably, for example, vinyltrimethoxysilane, etc. The compsn. ratio of the 1st and 2nd gaseous monomers is made preferably in a range of 4:1-20:1. The gaseous pressure in the case of performing polymn. is made within 0.03-3Torr range and the high-frequency output is made preferably within 0.03-0.5W/cm<2>. The thickness of the protective film layer is preferably within 30-1,000Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium having a plasma polymerized protective film layer and having excellent durability and corrosion resistance.

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 are provided on the magnetic layer to improve durability and corrosion resistance, and in recent years, it has been proposed to form a plasma polymerized protective film layer of an organic compound on the magnetic layer. ing. However, in the conventional method of forming a plasma-polymerized protective film layer of this type of organic compound on a magnetic layer, the deposition rate of the plasma-polymerized protective film layer is relatively slow;
It is still not possible to efficiently produce magnetic recording media with sufficient durability and corrosion resistance.

As a result of extensive research, the inventors have been proud of the current state of affairs and have found that silicon atoms are , a plasma r4vl of a mixed gas of a monomer gas of a silicon-based organic compound consisting of carbon atoms and hydrogen atoms or these and nitrogen atoms, and a monomer gas of a silicon-based organic compound containing silicon atoms and oxygen atoms and having an unsaturated bond. When the magnetic layer is exposed and subjected to plasma polymerization, the plasma polymerized protective film layer is deposited at a fast deposition rate, and the plasma polymerized protective film layer made of a dense and hard silicon-based organic compound is firmly adhered to the magnetic layer. The present inventors have discovered that the abrasion resistance is greatly improved, the durability is improved, and the corrosion resistance is also sufficiently improved.

In the present invention, the plasma polymerized protective film layer is formed on the magnetic layer by combining silicon atoms, carbon atoms, and hydrogen atoms, or a silicon-based organic compound monomer gas consisting of silicon atoms, carbon atoms, and hydrogen atoms, or these and nitrogen atoms, and silicon atoms and oxygen atoms. It is formed by plasma polymerizing a monomer gas of a silicon-based organic compound having an unsaturated bond and an unsaturated bond on the surface of the magnetic layer. Monomer gases of silicon-based organic compounds consisting of silicon atoms, carbon atoms, hydrogen atoms, or these and nitrogen atoms used to form this plasma-polymerized protective film layer include, for example, tetramethylsilane, hexamethyldisilazane, vinyl Trimethylsilane, trimethylsilylacetylene, etc. are preferably used, and as the monomer gas of a silicon-based organic compound containing a silicon atom and an oxygen atom and having an unsaturated bond, for example, vinyltrimethoxysilane, allyloxytrimethylsilane, etc. are preferably used. Ru.

In the monomer gas of these compounds, radicals are generated by high frequency, and the generated radicals react and polymerize to form a film. When performing this plasma polymerization, as mentioned above, silicon-based organic compounds containing silicon atoms, carbon atoms, hydrogen atoms, or these and nitrogen atoms, and silicon-based organic compounds containing silicon atoms and oxygen atoms and having unsaturated bonds are used. When a monomer gas of an organic compound is added and used, the deposition speed is increased by the action of the added monomer gas, a dense and hard plasma polymerized protective film layer is obtained, and the durability and corrosion resistance are sufficiently improved. In addition, when plasma polymerizing these monomer gases, if a carrier gas such as argon gas or helium gas is co-existed, the deposition rate will be 3 to 5 times (7) 7 degrees compared to when plasma polymerizing monomer gas alone. Therefore, it is preferable to carry out this process in the presence of a carrier gas. At this time, oxygen gas may be mixed with the carrier gas. Plasma polymerization is performed by adding a monomer gas of a silicon-based organic compound containing silicon atoms and oxygen atoms and having an unsaturated bond to a monomer gas of a silicon-based organic compound consisting of silicon atoms, carbon atoms, and hydrogen atoms, or these and nitrogen atoms. The composition ratio when performing this is a monomer gas of a silicon-based organic compound consisting of silicon atoms, carbon atoms, and hydrogen atoms, or these and nitrogen atoms, to a monomer gas of a silicon-based organic compound containing silicon atoms and oxygen atoms and having an unsaturated bond. It is preferable to keep the monomer gas ratio within the range of 4:1 to 20:1. If the monomer gas of the silicon-based organic compound having an unsaturated bond is too small, the deposition rate will not be so fast and the If it is too dense, a dense and hard plasma polymerized protective film layer cannot be obtained. Further, when a carrier gas is made to coexist with the monomer gas of these silicon-based organic compounds, the composition ratio thereof is preferably 4:1 in terms of the ratio of the carrier gas to the monomer gas of the silicon-based organic compound. If the amount of gas is too small, the deposition rate will decrease, and if it is too large, the amount of monomer gas will decrease, which will interfere with the plasma polymerization reaction.

When performing plasma polymerization, the gas pressure and high frequency output are such that the higher the gas pressure, the faster the deposition speed, but on the other hand, the monomer gas has a relatively low molecular weight and is plasma polymerized, making it difficult to obtain a hard protective film layer. If the gas pressure is lowered and the radio frequency output is increased, the deposition speed will be slower, but a relatively hard protective film layer made of polymer will be obtained. However, if the gas pressure is lowered and the radio frequency output is too high, the monomer gas will turn into powder. Because the plasma polymerized protective film layer is not formed due to
Within the range of 3 to 3 torr, and the high frequency output is 0.03 to 0.
, 5 W/ctAl, the gas pressure is 0.1-1 Torr, and the high frequency output is 0.0
More preferably, it is within the range of 5 to 0.3 W/cIl. The silicon-based organic compound plasma-polymerized protective film layer deposited by plasma polymerization in this manner is dense, has a low V, and has a small friction coefficient. Wear resistance and corrosion resistance are further improved. The thickness of such a plasma polymerized protective film layer of a silicon-based organic compound is preferably within the range of 30 to 1000. If the film thickness is too thin, the durability and corrosion resistance effects of this protective film layer may be insufficient. If the thickness is too large and the spacing loss is too large, the electromagnetic conversion characteristics will be adversely affected.

The magnetic layer is formed on the substrate using 7-Fe2O3 powder, Fe
Magnetic powder such as 3O4 powder, CO-containing 7-Fe2'03 powder, CO-containing Fe3O4 powder, Fe powder, CO powder, Fe-Ni powder, etc. is applied onto a substrate together with a binder component and an organic solvent, and then dried, or , CoXNi-F
e, , Co-Ni, Co-Cr, , Co-P, Co-N
It is formed by depositing a ferromagnetic material such as 1-P on a substrate by means such as vacuum evaporation, ion blasting, sputtering, or plating.

Magnetic recording media manufactured by this method include a variety of structures that come into sliding contact with a magnetic head, such as magnetic tapes based on synthetic resin films such as polyester films, magnetic disks and magnetic drums based on disks or drums, etc. It includes the form of

Next, embodiments of the invention will be described.

Example 1 Thickness 10t! The polyester film was loaded into a vacuum evaporation apparatus, and the cobalt was heated and evaporated under a vacuum of 5×10 −51 to 10 μm to form a ferromagnetic metal thin film layer of cobalt with a thickness of 1000 μm on the polyester film. Next, using the plasma polymerization apparatus shown in FIG. 1, the polyester film 1 on which the ferromagnetic metal thin film layer was formed was moved from the raw roll 3 to the circumferential side of the cylindrical can 4 in the reaction tank 2. It was set to be wound up on the winding roll 5. Then, monomer gas of tetramethylsilane was introduced through the gas introduction pipe 6 at a flow rate of 200 sec, and vinyltrimethoxysilane was introduced as an additive gas at 40 sec, and a high frequency of 13.56 MHz was applied at a gas pressure of 0.10 Torr and an output of 100 W. Plasma polymerization was performed for 1 minute to form a plasma polymerized protective film layer. Thereafter, the tape was cut to a predetermined width to produce a magnetic tape A in which a ferromagnetic metal thin film layer 10 and a plasma polymerized protective film layer 11 were sequentially laminated on a polyester film 1 as shown in FIG. The thickness of the plasma polymerized protective film layer at this time was 25
There were 0 people. In the figure, 8 is an exhaust system for reducing the pressure inside the reaction tank 1, and 9 is an AC power source for applying high frequency to the electrode 7.

Example 2 In the formation of the plasma polymerized protective film layer in Example 1, the same amount of hexamethyldisilazane was used instead of tetramethylsilane, and allyloxytrimethylsilane was used for 25 seconds instead of vinyltrimethoxysilane as an additive gas.
A magnetic tape was produced in the same manner as in Example 1 except that m was used. The thickness of the plasma polymerized protective film layer at this time was 30
There were 0 people.

Example 3 α-Fe magnetic powder 600 parts by weight Esresoku CN (manufactured by Tsukisui Kagaku Kogyo 80μ Co., Ltd., vinyl chloride-vinyl acetate copolymer) Pa7 Teso') S T 5250 (Dai 3o, manufactured by Nippon Ink Co., Ltd., urethane elastomer) ) Trifunctional low molecular weight unsocyanate compound manufactured by Nippon Polyurethane Industry Co., Ltd.) Methyl isobutyl ketone 4oo Toluene 4oon This composition was mixed and dispersed in a ball mill for 72 hours to prepare a magnetic paint. A magnetic layer was formed by coating on a polyester film having a thickness of 10 μm to a dry thickness of 4 μm and drying. Next, a plasma polymerized protective film layer was formed thereon in the same manner as in Example 1 to produce a magnetic tape.

Comparative Example 1 In the formation of the plasma polymerized protective film layer in Example 1, the addition of vinyltrimethoxysilane was omitted and the gas pressure was reduced to 0.
．． A magnetic tape was produced in the same manner as in Example 1 except that the thickness was changed from 101 to 0.08 torr. The thickness of the plasma polymerized protective film layer at this time is estimated to be 80 people.

Comparative Example 2 In the formation of the plasma polymerized protective film layer in Example 2, the same procedure as Example 1 was carried out except that the addition of allyloxytrimethylsilane was omitted and the gas pressure was changed from 0.101 torr to 0.08 torr. and made magnetic tape. The thickness of the plasma polymerized protective film layer in this case is determined to be 90 and 111.

Comparative Example 3 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.

In each Example and each Comparative Example, the deposition rate of the plasma polymerized protective film layer was measured, and the magnetic tape obtained in each Example and each Comparative Example was tested for durability and corrosion resistance. Durability tests were carried out on sapphire magnetic tapes
A sliding test was performed with a needle to measure the number of times it took for the plasma polymerized protective film layer to be scratched.A corrosion resistance test was performed by leaving the obtained magnetic tape at 60°C and 190% RH for 7 days. The maximum magnetic flux density was measured, and the deterioration rate was determined based on the value compared with the maximum magnetic flux density of the magnetic tape before being left as 100%.

The table below shows the results.

As is clear from Table 1, the magnetic tapes (Examples 1 to 3) obtained by the production method of the present invention all contained silicon-based organic compounds containing silicon atoms and oxygen atoms and having unsaturated bonds. Compared to magnetic tapes (Comparative Examples 1 and 2) and conventional magnetic tapes (Comparative Example 3), the deposition speed of the plasma polymerized protective film layer is faster and the deterioration rate is smaller. It can be seen that according to the manufacturing method of the present invention, a magnetic recording medium with excellent durability and corrosion resistance can be efficiently obtained with a fast deposition rate of the plasma polymerized protective film layer.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of a plasma polymerization 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), 1o...Ferromagnetic total refraction thin film layer (magnetic layer), 11...Plasma polymerized protective film layer, Δ...Magnetic tape (magnetic recording medium) Patent applicant Hitachi Maxell Co., Ltd.

Claims (1)

[Claims] 1. Form a magnetic layer on the substrate, then apply this magnetic layer to
Plasma of a mixed gas of a monomer gas of a silicon-based organic compound consisting of silicon atoms, carbon atoms, and hydrogen atoms, or these and nitrogen atoms, and a monomer gas of a silicon-based organic compound containing silicon atoms and oxygen atoms and having an unsaturated bond. A method for producing a magnetic recording medium, which comprises exposing a magnetic layer to a plasma-polymerized protective layer of a silicon-based organic compound on a magnetic layer.