JPH0357532B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Fields Magnetic recording media such as magnetic tapes and magnetic disks. Structure of conventional examples and their problems Iron, cobalt, nickel, alloys containing these as main components, or thin films of their oxides are formed into polyester films using vacuum film forming methods such as vacuum evaporation, sputtering, and ion plating. Ferromagnetic thin-film magnetic recording media formed on substrates made of polymer films such as polyimide films, non-magnetic metal thin plates, etc. can dramatically improve recording density compared to conventional coating-type magnetic recording media. Although this is possible, in order to achieve this high density, it is necessary to reduce the gap of the magnetic head and at the same time smooth the surface of the magnetic recording medium to reduce spacing loss as much as possible. However, if the surface is made too flat, it will cause problems in head touch and runnability, so it is necessary to solve this problem by controlling the fine shape of the surface. The surface properties of ferromagnetic thin-film magnetic recording media largely depend on the surface shape of the plastic film that is the substrate, since the magnetic layer thickness is very small, about 0.01 to 0.5 μm. Therefore, many proposals have been made regarding the surface properties of the film. Examples of this include JP-A-52-18770, JP-A-52-84264, and JP-A-53-84264.
Publication No. 116115, Japanese Patent Publication No. 128685, Japanese Patent Application Publication No. 1983-128685, Publication No.
They are described in JP-A-54-40883, JP-A-54-94574, JP-A-56-10455, JP-A-56-16937, and the like. In all of these examples, the surface shape is roughened relatively finely and uniformly, for example, by forming wrinkle-like protrusions, worm-like protrusions, or granular protrusions, thereby improving head touch and running properties. This is an attempt to improve. The surface condition shown in the above example is very effective in terms of head touch and head running properties at room temperature and humidity. However, it has the disadvantage that the cylinder part of the rotating head tends to generate noise in high humidity conditions such as 30°C and 80-90% R.H. One way to solve this problem is to use polyester film as the substrate.
A proposal has already been made in which the polyester oligomer contained therein is deposited as fine crystals on the substrate surface when forming a ferromagnetic layer in a vacuum, and a ferromagnetic metal thin film layer is formed on top of the fine crystals. In this case, the frequency of precipitation of oligomer crystals is highly dependent on location, and it is difficult to analyze oligomer crystals uniformly over the entire surface, which tends to cause uneven distribution depending on location. Therefore, there was a drawback that the envelope characteristics of the resulting magnetic recording medium were likely to be disturbed. Furthermore, it is known that a film in which a ferromagnetic thin film is formed on a polyester film with protruding thermoplastic particles on the surface as described in JP-A No. 53-107314 has good running properties and good image quality. There is. However, in this case, even if you try to improve the surface roughness of the magnetic recording medium to increase the recording density, if the surface roughness becomes 0.03 μm or less,
Stakes slip occurs and running performance deteriorates. OBJECTS OF THE INVENTION An object of the present invention is to easily obtain a metal thin film magnetic recording medium suitable for high-density recording, which improves squealing in high humidity and also improves reproduced image quality. Structure of the Invention The present invention provides a particle with a height of 30 mm with a core of ferromagnetic fine particles.
It is characterized in that a ferromagnetic metal thin film is formed on a plastic film substrate on which ^more than 1000 particle-like protrusions of ~500 Å are present on the surface. DESCRIPTION OF EMBODIMENTS FIGS. 1 and 2 show cross sections of embodiments of the magnetic recording medium of the present invention, and in the figures, 1,
1' is a plastic film substrate, 2, 2' are ferromagnetic fine particles, 3' is a binding resin for fixing the fine particles 2' onto the plastic film substrate 1', 4,
4' is a ferromagnetic metal thin film, and 5 and 5' are lubricant layers.
In FIG. 1, the fine particles 2 themselves form particulate protrusions and are attached to the plastic film substrate 1 by themselves.
In Fig. 2, fine particles 2'
Particulate protrusions are formed from the bonding resin 3' and the bonding resin 3'. Further, the lubricant layer 5 exists on the entire surface of the ferromagnetic metal thin film 4, but the lubricant layer 5' exists only in a specific portion on the ferromagnetic metal thin film 4'. The height of the particulate protrusions was measured using a high-precision stylus-type surface roughness measuring device (TALYSTEP-1, TAYLOR-
(manufactured by HOBSON), and is measured by JIS
Maximum surface roughness specified in B0601, Rmax
If the distance is expressed as the distance from the top of the uneven mountain to the bottom of the valley according to
Å, more preferably 50 to 300 Å. If the thickness is less than 30 Å, it is difficult to obtain a squeal prevention effect in high humidity, and if it exceeds 500 Å, the envelope is likely to be disturbed. The planar spread of the particulate projections is suitably 1 to 20 times, more preferably 2 to 10 times, their height. If it is 20 times or more, the anti-squeal effect in high humidity will be reduced. The density of particulate protrusions is 1000 per ^mm2 of surface.
It is appropriate to have at least 1,000 grooves, more preferably at least 2,500 grooves, and if there are less than 1,000 grooves, the squeal prevention effect will be reduced in high humidity. This density can be obtained by observing a minimum of 10 fields of view with a differential interference light microscope with a magnification of 400, or by observing a minimum of 10 fields of view with a scanning electron microscope with a magnification of 3000.
The number of particulate resin protrusions present within the field of view is calculated and converted to 1 mm ² . As the plastic film substrate, polyester films made of polyethylene terephthalate or copolymers or mixtures thereof, polyethylene naphthalate or copolymers or mixtures thereof, etc.
Polyimide film substrates such as polyesterimide and polyimide, aromatic polyamide film substrates, etc., which have particularly excellent surface smoothness,
Taking polyester film substrates as an example, there are those with good smoothness that contain almost no microprotrusions made of polymerization catalyst residue, or with microprotrusions that are several hundred Å or less in size, and those with the aforementioned wrinkles and earthworms. It is suitable that the surface has uniform fine protrusions in the shape of particles or grains, and the surface roughness is several hundred angstroms or less. Methods for forming particulate protrusions on these film substrates include, for example, applying and drying a dispersion in which ferromagnetic fine particles are dispersed in a solvent using a surfactant, or dispersing them in a resin solution. There is a method in which a dispersion liquid in which ferromagnetic fine particles are dispersed is applied and dried on the surface of a film substrate. The resins used in the present invention include various polyesters such as thermoplastic resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or copolymers thereof, nylon 6, nylon 66, and nylon.
Various polyamides, polycarbonates, polyarylates, polysulfones, polyethersulfones, polyphenylene oxides, phenoxy resins, etc. made of 610, nylon 11, nylon 12, or copolymers thereof are most suitable, but other resins, such as polystyrene, polyacrylate,
Polyvinyl chloride, etc. can be used. In addition to thermoplastic resins, crosslinkable resins such as epoxy, phenol, and silicone can also be used. The ferromagnetic fine particles used in the present invention include cobalt, nickel, iron, iron-nickel alloy, cobalt-nickel alloy, iron-cobalt alloy, and cobalt-nickel alloy.
Examples include fine metal particles such as chromium alloy, fine ferrite particles such as magnetite, manganese ferrite, iron-zinc ferrite, and manganese-zinc ferrite. Surfactants used to overcoat ferrite particles include oleic acid, sodium oleate,
Long chain fatty acids, long chain sulfonic acids, and salts thereof are used. Furthermore, commercially available magnetic fluids are ones in which magnetite or the like is dispersed in paraffin with a surfactant, and therefore can be used in the present invention. Examples of ferromagnetic thin films include Co, Ni, and Fe, which are formed by oblique deposition or vertical deposition.
Metal thin films mainly composed of ferromagnetic metals such as ferromagnetic metal thin films, and metal thin films mainly composed of these alloys (e.g. Co-Cr perpendicular magnetization films) can be used. For the purpose of improving wear resistance, it is desirable to use an oxygen-containing ferromagnetic metal thin film obtained in an atmosphere dominated by oxygen gas during vapor deposition. The oxygen content is suitably at least 3% or more, preferably 5% or more in terms of atomic ratio to the ferromagnetic metal or nonmagnetic metal near the surface of the film substrate. In addition, if necessary, prior to forming the ferromagnetic metal thin film, a thin film with a mechanical reinforcing effect, such as Ti, Cr, etc.
It is also possible to form a thin film of an oxygen-containing metal such as Ni or a thin film of an oxide such as Al ₂ O ₃ or SiO ₂ . By combining the ferromagnetic metal thin film containing oxygen as described above, or the above-mentioned non-magnetic metal layer formed under it as necessary, and particulate protrusions, it is possible to greatly improve the still life. becomes. Note that the still life is also related to the thickness of the ferromagnetic metal thin film and decreases rapidly when the thickness is less than 400 Å, so it is desirable that the thickness is 400 Å or more. By allowing a lubricant to exist on the surface of the ferromagnetic thin film layer, it is possible to further enhance the running property improvement effect based on the shape of the particulate protrusions. This further ensures complete prevention of squealing in high humidity environments. The lubricant layer on the ferromagnetic metal thin film may be present on the entire surface as shown in FIG. 1, or may be present locally as shown in FIG. In addition to coating or vapor-depositing the film directly on the surface of the ferromagnetic metal thin film, other methods include coating or vapor-depositing it on the back side of the magnetic recording medium and transferring it to the surface of the ferromagnetic metal thin film during stacking (winding) of the magnetic recording medium. A method of forcing it is also possible. It is also possible to use a resin binder or the like to firmly adhere the lubricant layer. As the lubricant, fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins, silicones, fluorine surfactants, inorganic lubricants, etc. can be used. The amount of lubricant present is 0.5 to 500 mg ^per square meter of surface, more preferably 5 to 500 mg.
200mg is appropriate. Fatty acids include lauric acid, myristic acid,
Those having 12 or more carbon atoms such as palmitic acid, stialic acid, behenic acid, oleic acid, linoleic acid, and linolenic acid can be used. Fatty acid esters include ethyl stearate, butyl stearate, amyl stearate,
Stearic acid monoglyceride, palmitic acid monoglyceride, oleic acid monoglyceride, pentaerythritol tetrastearate, etc. can be used. Fatty acid amides include caproic acid amide, capric acid amide, lauric acid amide, palmitic acid, acid amide, stearic acid amide, behenic acid amide, oleic acid amide, linoleic acid amide, methylene bisstearic acid amide, and ethylene bis stearic acid amide. etc. can be used. Metal soaps include zinc, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, etc.
Salts, lauryl, palmityl, myristyl, stearyl, with lead, nickel, cobalt, iron, aluminum, magnesium, strontium, copper, etc.
Salts of sulfonic acids such as behenyl, oleyl, linole, and linolenic with the various metals mentioned above can be used.
Examples of aliphatic alcohols include cetyl alcohol,
Stearyl alcohol etc. can be used. As paraffin, n-ocdecane, n-nonadecane, n-tridecane, n-docosane, n-
Saturated hydrocarbons such as dotriacontane can be used. As silicones, polysiloxanes in which hydrogen is partially substituted with alkyl groups or phenyl groups, and those modified with fatty acids, aliphatic alcohols, acid amides, etc. can be used. Examples of fluorine-based surfactants include salts of perfluoroalkyl carboxylic acids and perfluoroalkyl sulfonic acids with sodium, potassium, magnesium, zinc, aluminum, iron, cobalt, nickel, etc., perfluoroalkyl phosphate esters, and perfluoroalkyl phosphates. Alkyl betaine, perfluoroalkyltrimethylammonium salt, perfluoroethylene oxide, perfluoroalkyl fatty acid ester, etc. can be used. Examples of the inorganic lubricant include graphite powder, molybdenum disulfide powder, tungsten disulfide powder, molybdenum selenide powder, tungsten selenide powder, calcium fluoride powder, and the like. Rust is prevented by known means on the front surface, the back surface, or the vicinity thereof of the magnetic recording medium of the present invention, the air gap in the ferromagnetic metal thin film, the interface between the ferromagnetic metal thin film and the plastic film substrate, the inside of the plastic film substrate, etc. Various additives such as antistatic agents, antistatic agents, and antifungal agents can be added as necessary. Next, a more specific example will be explained. Example 1 The following composition solution was coated on a smooth polyethylene terephthalate biaxially stretched film substrate that had significantly suppressed protrusions caused by polymerization catalyst residue and had a surface roughness of 30 Å or less, and was continuously coated and dried to a thickness of about 10 μm. death,
A long film sample was obtained which had about 500,000 particles/mm ² of particle-like protrusions made of magnetite with a particle height of about 50 Å on the surface. This sample is designated as A. Paraffin-based magnetite-based magnetic fluid (50wt% magnetite, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)
1g isooctane 2000g Example 2 When the liquid composition was changed to the following in Example 1, a sample having about 100,000/mm ² particulate protrusions made of manganese zinc ferrite and having a particle height of about 200 Å was obtained. This sample is designated as B. Paraffin-based manganese-zinc magnetic fluid (manganese-zinc ferrite 50wt%, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 1 g Isooctane 1000 g Example 3 When the liquid composition in Example 1 is changed to the following, it consists of iron-zinc ferrite. Particle height approx.
A sample with approximately 300,000 particle projections/mm ² of 150 Å was obtained. This sample is designated as C. Paraffin-based iron-zinc magnetic fluid iron-zinc ferrite 45wt%, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)
1g Toluene 1500g Example 4 When the liquid composition in Example 1 was changed to the following, particle protrusions with a height of about 300 Å with iron-nickel as the core and polyester resin as the bonding resin were formed.
A sample with 200,000 pieces/mm ² was obtained. This sample is designated as D. Iron-nickel fine particles 1g Polyester (Vylon #200, manufactured by Toyobo Co., Ltd.)
1g Toluene 1000g Example 5 When the liquid composition in Example 1 is changed to the following, approximately 50,000 particulate protrusions with a particle height of approximately 400 Å each having a fine particle of nickel as a core and a polyester resin as a bonding resin are produced. A sample with mm ² was obtained. This sample is designated as E. Nickel fine particles 1g Polyester (Vylon #200) 1g Toluene 200g Example 6 When the liquid composition in Example 1 is changed to the following, the particle height is approx. with cobalt fine particles as the core and phenoxy resin as the binding resin. 350Å
A sample having about 100,000 particulate protrusions/mm ² was obtained.
This sample is designated as F. Cobalt fine particles 0.5g Phenoxy resin (manufactured by Tomoe Kogyo Co., Ltd.) 0.5g Cellosolve acetate 1000g Example 7 Made of polyethylene terephthalate containing almost no fine particles due to polymerization catalyst residue, a thickener was added to the surface during film formation and stretching. A biaxially stretched polyethylene terephthalate film, on which a thin layer of different polymers consisting of fine wavy irregularities with a surface roughness of 100 Å was formed by coating and curing a liquid mainly containing modified silicone emulsion, was used as a plastic film substrate. Samples obtained by performing the same coating treatment as in Examples 1 to 6 are designated as G, H, I, J, K, and L, respectively. The particulate projections formed on the surfaces of these samples were almost the same as those of the corresponding samples A to F, respectively. Example 8 When only the amount of magnetite-based magnetic fluid was changed to 0.001 g in Example 1, a sample having 500 particulate projections/mm ² of magnetite with a particle height of 50 Å was obtained. This sample is designated as M. Comparative Example 1 The plastic films used in Examples 1 to 6 and 8 and Example 7 were used as samples N and O, respectively.
shall be. Example 9 Each of the above samples A to O was sequentially connected, and a Co-Ni ferromagnetic metal thin film (Ni = 20 wt%, film thickness 1000 Å) was deposited on each surface by continuous vacuum oblique evaporation method in the presence of a trace amount of oxygen. was formed. The oxygen content of the magnetic layer was 5% in terms of atomic ratio to the metal. after that,
Apply various lubricant solutions to the surface of each sample and slit them to a specified width to make magnetic tape.
Using a prototype video recorder in an environment of %RH, we measured the noise condition and envelope of the rotating head cylinder, as well as the still life. As a comparative example, sample 0 was heat-treated before vapor deposition to precipitate polyester oligomer crystals on the surface, and then vapor-deposited in the same manner as described above.
A lubricant solution was applied to a magnetic tape with a density of approximately 100,000 particles/mm ² ), and a magnetic tape was formed without applying a lubricant solution after vapor deposition for specific samples A to O above. The above measurements were also carried out on the tape. These results are shown in the following table.

【table】

[Table] Effects of the Invention As is clear from the above description, the magnetic recording medium of the present invention uses ferromagnetic fine particles coated with a surfactant to form particulate protrusions with a height of 30 to 500 Å on a plastic film substrate. 1000 pieces/ ^mm2
The above-mentioned particles can be uniformly dispersed without agglomeration to form a ferromagnetic metal thin film, and since a lubricant layer is formed on the ferromagnetic metal, it does not make noise even in high humidity. It has a good envelope, exhibits stable running properties, and has a good still life even in high humidity conditions, making it of very high practical value.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of magnetic recording media according to the present invention, respectively. 1, 1'...Plastic film substrate, 2,
2'...Nucle of ferromagnetic fine particles, 4,4'...Ferromagnetic metal thin film, 5,5'...Lubricant layer.

Claims (1)

[Claims] 1. 1000/1000 particulate protrusions with a height of 30 to 500 Å each having a core of ferromagnetic fine particles coated with a surfactant.
1. A magnetic recording medium characterized in that a ferromagnetic metal thin plate is formed on a plastic film substrate having an area of 2 mm ² or more on the surface, and a lubricant layer is formed on the ferromagnetic metal thin plate. 2. The magnetic recording medium according to claim 1, wherein the ferromagnetic fine particles are selected from ferromagnetic metals and ferrite particles.