JPH0479065B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium comprising a magnetic metal thin film formed by a vapor deposition method as a magnetic recording layer, and more particularly to a magnetic recording medium with excellent durability, running characteristics, and weather resistance, and a method for manufacturing the same. Conventionally, magnetic recording media include r-Fe ₂ O ₃ on a non-magnetic support, r-Fe ₂ O ₃ doped with Co,
Fe ₃ O ₄ , Co-doped Fe ₃ O ₄ , r-Fe ₂ O ₃ and
Powdered magnetic materials such as Fe ₃ O ₄ bertolide compounds, magnetic powders such as CrO ₂ , or ferromagnetic alloy powders are combined with organic materials such as vinyl chloride-vinyl acetate copolymers, styrene-butadiene copolymers, epoxy resins, polyurethane resins, etc. Coating-type products have been widely used, in which the material is dispersed in a binder and then applied and dried. In recent years, with the increasing demand for high-density recording, vapor deposition such as vacuum evaporation, sputtering, ion plating, or electroplating,
So-called binder-free magnetic recording media, which do not use a binder and which use a ferromagnetic metal thin film formed by a plating method such as electroless plating as a magnetic recording layer, are attracting attention, and various efforts are being made to put them into practical use. There is. Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning required for high-density recording leads to a reduction in signal output, which has reached its limit. Moreover, the manufacturing process is complicated and has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention. In a non-binder type magnetic recording medium, a ferromagnetic metal having a saturation magnetization larger than that of the oxide is formed as a thin film without containing a non-magnetic substance such as a binder.
It has the advantage that it can be made ultra-thin for high-density recording, and its manufacturing process is simple. As one of the requirements for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally. There are great expectations for non-binder type magnetic recording media that can be easily made small and thin and have a high saturation magnetic flux density. In particular, the vapor deposition method is very advantageous because it does not require drainage treatment as is the case with plating, the manufacturing process is simple, and the film deposition rate can be increased. Furthermore, major problems concerning magnetic recording media made of ferromagnetic metal thin films include strength against corrosion and abrasion, and running stability. In the process of recording, reproducing, and erasing magnetic signals, magnetic recording media are subjected to high-speed relative motion with the magnetic head, but in this case, the traveling must be smooth and stable, and at the same time, contact with the head must be maintained. There shall be no wear or damage due to It is also required that the recorded signals should not be reduced or lost due to changes over time due to rust or the like while the magnetic recording medium is being stored. Providing a protective layer has been considered as a way to improve durability and weather resistance, but there is a constraint that the thickness of the protective layer cannot be increased due to spacing loss between the head and the magnetic layer, so it is difficult to increase the thickness of the protective layer itself. It is also necessary to provide durability and weather resistance. The protective layer was composed of hard metals such as rhodium and chromium, or hard inorganic materials such as WC, TiO ₂ and CaF ₂ , or lubricants and polymeric agents. However, by simply providing these protective layers, it has not been possible to obtain a magnetic recording medium with sufficiently satisfactory running characteristics and durability. The main reason for this is that the peeled off pieces of the hard metal or hard inorganic material also cause scratches on the recording medium.Also, even if the protective layer is made of polymer or lubricant, the metal magnetic thin film and the protective layer This was because the bond at the interface was weak, and the running characteristics and wear resistance characteristics deteriorated significantly over time. Furthermore, JP-A No. 50-33806 discloses a method of nitriding the vicinity of the surface of the magnetic layer by direct current glow discharge in nitrogen, but merely nitriding the surface of the magnetic layer does not improve the running characteristics. In order to produce a protective effect by the surface nitride layer, it was necessary to perform glow discharge treatment for a long time of 10 minutes to 2 hours to form a sufficient metal nitride layer. In addition, as a method of forming a protective oxide layer by oxidizing the magnetic layer, a method of placing a ferromagnetic metal thin film under appropriate temperature and humidity and oxidizing its surface (see Japanese Patent Publication No. 42-20025) , a method in which an alloy magnetic thin film is brought into contact with nitric acid and then heat treated to form an oxide layer on the surface, and then a lubricant is impregnated (see British Patent No. 1265175); A method has been known in which the film is formed by treatment with an aqueous solution of an organic chelating agent and then heat treatment in an oxygen atmosphere. With these processing methods, it is difficult to create a thin and uniform oxide layer, and since aqueous solutions are used, it is necessary to break the vacuum after forming the metal thin film, making continuous processes impossible, and the processing time is long. And it was complicated. The present inventors have made extensive efforts to solve the above-mentioned drawbacks of the prior art and to develop a non-binder type magnetic recording medium that has excellent durability, runnability, and weather resistance, and as a result, they have arrived at the present invention. Ivy. That is, in a method of forming an organic protective lubricant layer on a magnetic metal thin film layer to impart a protective lubricant effect, the present inventors coated the surface of the magnetic metal thin film layer with silicic acid before forming the organic protective lubricant layer. The present inventors have discovered that durability, runnability, and weather resistance can be significantly improved by forming a silicon compound layer by exposing it to glow discharge plasma generated in a vacuum atmosphere containing ester gas, and have arrived at the present invention. The present invention eliminates the drawbacks of the prior art described above,
The object of the present invention is to provide a binder-free magnetic recording medium that has excellent durability, runnability, and weather resistance, and a method for manufacturing the same. The object of the present invention is to provide a magnetic recording medium comprising a magnetic metal thin film layer, a silicon compound layer, and a protective lubricant layer made of a higher fatty acid, a fatty acid ester, or a combination thereof, respectively laminated on a nonmagnetic medium. After forming a magnetic metal thin film layer on a non-magnetic substrate by a vapor deposition method, the surface of the magnetic metal thin film layer is exposed to glow discharge plasma generated in a vacuum atmosphere containing silicate ester gas to form the magnetic metal. A magnetic recording medium characterized in that a silicon compound layer is formed on the surface of a thin film layer, and then at least one of a higher fatty acid and a fatty acid ester is vapor-deposited on the silicon compound layer in a vacuum atmosphere to form a protective lubricant layer. This is achieved by the manufacturing method. Embodiments of the present invention will be described below. FIG. 1 shows one of the apparatuses for carrying out the method of the present invention.
This shows an aspect, and the magnetic recording medium manufacturing apparatus 1 includes:
Substrate delivery chamber/winding chamber 2 , glow discharge pretreatment chamber 3 ,
A magnetic metal thin film layer deposition chamber 4 , a silicate ester glow discharge treatment chamber 5 , and a protective lubricant layer deposition chamber 6 are successively connected to each other through a slit 9 for passing the substrate, which is limited to a small opening area. . Note that each of the chambers 2 to 6 communicates with independent exhaust systems 7a to 7e via conduits 8a to 8, so that the respective vacuum level (usually 10 ^-1 to 10 ^-6 Torr) can be maintained. It's getting old. In the delivery/winding chamber 2, a pull-out roller 11 disposed near a roll 10 consisting of a rotatably supported non-magnetic and flexible strip-shaped substrate W is driven to extract the substrate W from the roll 10. is continuously fed into the glow discharge pretreatment chamber 3 ,
Ar gas supplied through the Ar gas introduction tube 12 causes glow discharge in a vacuum atmosphere of about 10 ^-2 Torr by the electrode 13 to which an AC high voltage (for example, about 1 kV) is applied, and the The surface of the substrate W is cleaned and activated, and the adhesion to the magnetic metal thin film layer in the next step is improved. The substrate W that has passed through the glow discharge pretreatment chamber 3 is held by the lower outer peripheral surface of a cooling can 15 that is rotatably supported via a plurality of guide rollers 14 in the magnetic metal thin film deposition chamber 4 . After the running direction is reversed, it is sent into the silicate ester glow discharge treatment chamber 5 . The magnetic metal thin film deposition chamber 4 is heated under an atmosphere maintained at a fairly high degree of vacuum (for example, 10 ^-5 Torr) in the hearth 17 using an electron beam heating means 16 consisting of an electron gun and a power source. body evaporation source 18
(For example, Co material, Ni material, Fe material, etc.) is heated and evaporated, and the vapor flow V is usually deposited on the substrate on the creeling can 15 at an incident angle of about 40° to 90°. to form a magnetic metal thin film (A in Figure 2).
This is where it forms. The incident angle is appropriately set depending on the arrangement positions of the hearth 17 and the mask 19. Further, in this embodiment, a vapor deposition method is shown as a method for forming the magnetic metal thin film layer, but of course a method such as a sputtering method may also be used. The silicate ester glow discharge treatment chamber 5 is provided for generating glow discharge plasma in a vacuum atmosphere containing silicate ester gas to form a silicon compound layer on the surface of the magnetic metal thin film. The silicate ester gas is introduced through the gas introduction pipe 20 so as to have a desired gas partial pressure or flow rate. Note that if the partial pressure of the silicate ester gas is lower than the desired vapor pressure, measures such as heating the gas introduction pipe 20 and the silicate ester gas storage container may be taken as appropriate. Further, a reactive gas introduction pipe 21 is provided for mixing a reactive gas in addition to the silicate ester gas. Note that glow discharge plasma is generated in a vacuum atmosphere containing silicate ester gas by applying high frequency power (for example, 13.56 MHz,
150W) is applied. The coil 24 is installed near the base coated with the magnetic metal thin film layer. The substrate coated with the magnetic metal thin film layer sent into the silicate ester glow discharge treatment chamber 5 is
When exposed to glow discharge plasma generated in an atmosphere containing the silicate ester gas and moved, a silicon compound layer (B in FIG. 3) is formed on the surface of the magnetic metal thin film layer. Next, in the protective lubricant layer deposition chamber 6 ,
The vapor flow obtained by heating and evaporating higher fatty acids, fatty acid esters, or a combination thereof using resistance heating means 26 at a vacuum degree of about 10 ^-4 Torr moves the magnetic metal thin film layer and the silicon compound. A protective lubricating layer (FIG. 4C) of a desired thickness is deposited on the silicon compound layer B by vapor deposition on the coated substrate. Thereafter, the substrate is covered with the magnetic metal thin film layer, the silicon compound layer, and the protective lubricant layer, and is returned to the delivery/winding chamber 2, where the wrinkles are properly corrected by the expander roller 27. The film is wound up into a roll 28 to complete a series of thin film forming steps. Note that the base body running in the protective lubricant layer deposition chamber 6 may be provided with a means such as a cooling can as in the magnetic metal thin film layer deposition chamber 4 , or the vapor flow may be applied to the surface of the base body. Oblique incidence may also be used. Note that this embodiment is just one example, and the present invention is not limited to this embodiment. The magnetic metal materials used in the present invention include:
Metals such as Fe, Co, Ni, or Fe−Co, Fe−
Ni, Co-Ni, Fe-Co-Ni, Fe-Rh, Fe-Cu,
Co-Cu, Co-Au, Co-Y, Co-La, Co-Pr,
Co−Gd, Co−Sm, Co−Pt, Ni−Cu, Mn−
Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni
−Cr, Fe−Co−Cr, Ni−Co−Cr, Fe−Co−Ni
-It is a ferromagnetic alloy whose main component is Cr. Particularly preferred is Co or an alloy containing 75% by weight of Co. Furthermore, as additives, W, Mo, Ta, Mg, Si,
It may also contain a small amount of Al or the like. Also, C, B, O, N,
It may also contain a small amount of nonmetallic components such as P. These may be included in the base material for thin film formation, and
It may be added as a component of the gas atmosphere during thin film formation. For example, the formation of the magnetic metal thin film layer in the magnetic metal thin film layer deposition chamber 4 may be carried out in an oxygen atmosphere into which some oxygen gas is introduced. The thickness of the magnetic metal thin film layer is generally about 100% because it needs to be thick enough to provide sufficient output as a magnetic recording medium and thin enough to perform high-density recording.
From 0.02μm to 20000Å, preferably from 0.05μm
It is 10000Å. Further, the magnetic metal thin film layer may be a single layer or may be composed of a multilayer film of two or more layers. Furthermore, in the case of a multilayer structure, a nonmagnetic intermediate layer may be provided between the layers. A nonmagnetic underlayer may be provided between the nonmagnetic substrate and the magnetic metal thin film layer. Furthermore, magnetic metal thin film layers may be provided on both sides of the nonmagnetic substrate. The vapor deposition method in the present invention is
In addition to the usual vacuum evaporation described in the specification of U.S. Pat. It also includes a method of forming a thin film on a supporting substrate in an atmosphere, for example, as described in Japanese Patent Application Laid-Open No.
Field vapor deposition method as shown in specification No. 51-149008, Japanese Patent Publication No. 43-11525, Japanese Patent Publication No. 46-20484,
Special Publication No. 47-26579, Special Publication No. 49-45439, Japanese Patent Publication No.
No. 49-33890, JP-A-49-34483, JP-A-49-
An ionized vapor deposition method as disclosed in Japanese Patent No. 54235 can also be used in the present invention, and other methods such as a sputtering method and a plasma polymerization method can also be applied. In addition, the substrate used in the present invention includes polyethylene terephthalate, polyimide, polyamide,
Plastic bases such as polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate are preferred. Furthermore, Al, Cu, SUS
Non-magnetic metals such as, or inorganic substrates such as glass and ceramics can also be used. Particularly in the present invention, the above-mentioned flexible plastic base having a surface roughness (ra) of 0.012 μm or less is preferred. Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid. Examples of fatty acid esters include methyl stearate, ethyl palmitate, and stearic acid monoglyceride. The aforementioned protective lubricant layer can also be formed by sequentially depositing various materials by arranging a plurality of cooling cans in parallel. In either vapor deposition method, the total thickness of the protective lubricant layer is preferably in the range of 20 to 500 Å, more preferably 20 to 300 Å. The silicon compound layer in the present invention is a silicon compound layer deposited on the surface of the magnetic metal thin film by exposing the surface of the magnetic metal thin film to glow discharge plasma generated in a vacuum atmosphere containing silicate ester gas. , made of silicon oxide such as SiO ₂ .
The thickness of the silicon compound layer in the present invention is preferably 100 Å or less. Particularly preferably, the thickness is 10 Å or less. The silicon compound layer in the present invention does not necessarily have to form a uniform continuous film. For this reason, it is difficult to define the film thickness in a strict sense.
The film thickness in this specification means the average film thickness obtained by converting deposits into film thickness. Since the silicon compound layer in the present invention is extremely thin, it is difficult to clearly define the state of the coating. It is preferable that the coating state be such that the magnetic element, which is the main component constituting the metal thin film layer, and the silicon element and the oxygen element are detected at the same time. That is, from the viewpoint of Auger electron analysis, it is desirable that a surface state is formed in which a magnetic element, which is the main component of the magnetic metal thin film layer, a silicon element, and an oxygen element are mixed. Although the role of the silicon compound layer in the present invention is not necessarily clear, it enhances the function of retaining the organic protective lubricant layer formed subsequent to the formation of the silicon compound layer on the magnetic metal thin film layer. . In particular, in the magnetic metal thin film layer surface-treated by the method of the present invention, the silicon compound is uniformly precipitated even on the surface irregularities and the gaps between the columnar structures, so that the retaining function of the protective lubricant layer described above can be further improved. In addition, even if the silicon compound layer in the present invention is used in a very small amount, it can greatly improve various practical properties as a magnetic recording medium such as durability, running characteristics, and weather resistance, so spacing loss is small and electromagnetic conversion properties are improved. An excellent magnetic recording medium can be obtained, and its practical value is great. In the present invention, glow discharge treatment in a vacuum atmosphere containing silicate ester gas is performed by mixing appropriate amounts ^of silicate ester gas and reaction gas, and
The magnetic metal thin film layer is exposed to glow discharge plasma generated by maintaining a vacuum of 10 ^-1 Torr and applying power for glow discharge formation to the discharge electrode.
A silicon compound is formed on the surface. Preferred examples of the silicic acid ester gas include tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane, and tetrabenzyloxysilane. Particularly preferred is tetraethoxysilane. The reactive gas is preferably one that stabilizes the glow discharge and assists in the decomposition of the silicate ester; for example, oxygen, water vapor, etc. are preferable. To generate glow discharge, high frequency power, DC power, AC power, microwave power, etc. are required, but considering ease of handling, approximately 13.56 MHz is required.
High frequency power or direct current power is particularly preferred. When using high frequency power, 5×10 ^-5 to 6×10 ^-2 Torr
It is possible to cause glow discharge at a vacuum degree of . Also, when using DC power, 0.02 to 0.5 Torr
Glow discharge occurs at a certain degree of vacuum. As the discharge electrode, a coil-shaped, rod-shaped, net-shaped electrode, etc. may be provided in the vacuum chamber. Alternatively, a so-called electrodeless discharge in which an electrode is provided outside the vacuum chamber may be used. Hereinafter, the novel effects of the present invention will be clarified based on Examples. Example 1 Magnetic recording medium manufacturing apparatus 1 as shown in FIG.
A 25μ thick polyethylene terephthalate film substrate was placed in a vacuum evaporator at an angle of 60° to the evaporation source, and the temperature was set at 1×10 ^-5 Torr.
2000 Å of 99.99% cobalt metal was deposited at a rate of 200 Å/sec by electron beam heating at a vacuum degree of . Next, tetraethoxysilane gas and oxygen gas were introduced, and the partial pressure of Cl was maintained at approximately 1:1 at 6×
The surface of the cobalt deposited layer was exposed to glow discharge plasma generated with 200 Watts of high frequency power in an atmosphere of 10 ^-4 Torr for about 1 minute to form a SiO ₂ film with a thickness of about 8 Å. Thereafter, behenic acid was heated to 150 Å at a rate of 20 Å/sec using a resistance heating method in a vacuum of 1 × 10 ^-4 Torr.
Å was deposited. The tape was then slit into 1/2-inch width tapes, which were incorporated into the cassette of a small VHS VTR and evaluated as a magnetic tape. The recording medium thus produced was evaluated for durability, runnability, and weather resistance. Durability was evaluated by measuring the time required for the playback output signal to be reduced by half after the tape stopped running in a small VHS type VTR device, that is, the still durability time. The running characteristics were evaluated using a small VHS type VTR device.
After repeatedly running the tape 100 times, the number of scratches that could be observed with the naked eye in the width direction of the tape was counted. Note that a Matsushita Electric Industrial NV-8200 VTR device was used for evaluation of still durability time and scratches. Weather resistance was evaluated by comparing the rate of decrease in magnetization (demagnetization) after being kept in a thermostat at 60°C and 90% RH for two weeks. Table 1 shows still durability time, number of scratches, and demagnetization. For comparison, Table 1 also shows the untreated case without a protective lubricant layer (a) and the untreated case with a protective lubricant layer (b). In case (b), the protective lubricant layer has the same thickness of behenic acid. Here, untreated means that the silicon compound layer is not provided. In the case of (c) according to the present invention, remarkable improvements in still durability characteristics, scratch resistance characteristics, and weather resistance were observed compared to other materials.

[Table] As described above, according to the present invention, a magnetic recording medium with excellent durability, runnability, and weather resistance can be obtained, and its practical effects are extremely large. In Example 1, glow discharge plasma was generated by applying high frequency power, but the same effect was confirmed by applying DC voltage.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a main part of an example of a magnetic recording medium manufacturing apparatus used in the present invention, and FIGS.
FIG. 4 is a schematic cross-sectional view of a magnetic recording medium according to the present invention. In the figure, 2 is a substrate delivery and winding chamber, 3 is a glow discharge pretreatment chamber, 4 is a magnetic metal thin film layer deposition chamber, 5 is a silicate ester glow discharge treatment chamber, 6 is a protective lubricant layer deposition chamber, and W is a substrate. be.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic metal thin film layer, a silicon compound layer, and a protective lubricant layer made of higher fatty acids, fatty acid esters, or a combination thereof, respectively laminated on a nonmagnetic substrate. . 2. After forming a magnetic metal thin film layer on a non-magnetic substrate by a vapor deposition method, the surface of the magnetic metal thin film layer is exposed to glow discharge plasma generated in a vacuum atmosphere containing silicate ester gas. A silicon compound layer is formed on the surface of the magnetic metal thin film layer, and then at least one of a higher fatty acid and a fatty acid ester is deposited on the silicon compound layer in a vacuum atmosphere to form a protective lubricant layer. A method for manufacturing a magnetic recording medium.