JPH0132576B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to 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 made into polyester films using vacuum film forming methods such as vacuum evaporation, sputtering, and ion plating. , polymer films such as polyimide films,
Ferromagnetic thin-film magnetic recording media formed on substrates made of non-magnetic metal thin plates, etc. can dramatically improve recording density compared to conventional coating-type magnetic recording media. To achieve this, it is necessary to reduce the gap of the magnetic head and to smooth the surface of the magnetic recording medium to reduce spacing loss as much as possible. However, if the surface is too flattened, 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 are such that the magnetic layer thickness is 0.01 to 0.5μ.
Since it is very small, about m, it is highly dependent on the surface shape of the plastic film that is the substrate. Therefore, many proposals have been made regarding the surface properties of films. An example of this is JP-A-52
-18770 Publication, JP-A-52-84264, JP-A-Sho
54-40883, JP 53-116115, JP 53-128685, JP 54-94574,
It is described in JP-A-56-10455, JP-A-56-16937, etc. In all of these examples, the surface shape is roughened relatively finely and uniformly, for example, by forming wrinkle-like protrusions, thereby improving head touch and runnability all at once. The surface condition seen in the above example can be obtained by touching the head at normal temperature and humidity.
It is very effective in terms of head running properties. However, it has the disadvantage that the cylinder part of the rotating head tends to crack at high temperatures 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 been made to deposit the polyester oligomer contained therein as fine crystals on the substrate surface when forming a ferromagnetic layer in a vacuum, and then form a ferromagnetic metal thin film layer thereon. In this case, the frequency of precipitation of oligomer crystals is highly dependent on location, making it difficult to precipitate oligomer crystals in an even distribution 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. In addition, 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-53-107314,
It is known that at normal temperature and humidity, the running properties are good and the image quality is also good. However, in this case, even if we try to improve the surface roughness of the magnetic recording medium in order to increase the recording density, the surface roughness is only 0.03 μm.
If it is less than m, stick slip will occur at room temperature and humidity, resulting in poor running performance. OBJECTS OF THE INVENTION It is an object of the present invention to provide a metal thin film magnetic recording medium suitable for high-density recording, which has improved noise performance in high humidity and improved reproduced image quality. Structure of the Invention The magnetic recording medium according to the present invention has particle-like protrusions with a particle height of 90 to 500 Å on the surface of at least 1000 pieces/mm ² with a core of fine particles made of a hydrolysis product of metal alkoxide and a resin as a binder. It is characterized in that a ferromagnetic metal thin film is formed on the plastic film surface, and a lubricant is provided on the ferromagnetic metal thin film. DESCRIPTION OF EMBODIMENTS Figures 1 and 2 show a cross section of an embodiment of the magnetic recording medium of the present invention, in which 1 and 1' are plastic films, and 2 and 2' are plastic films made of metal alkoxide hydrolysis products. The core of fine particles consisting of, 3,
3' is the nucleus 2, 2' with plastic film 1, 1'
A bonding resin for fixing on top, 4 and 4' are ferromagnetic metal thin films, and 5 and 5' are lubricants. In FIG. 1, the lubricant 5 is present on the entire surface of the ferromagnetic metal thin film 4, but in FIG. 2, the lubricant 5' is present only on a specific portion of 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 BO601, R _nax
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 it is less than 30 Å, it is difficult to obtain the anti-sagging effect in high humidity, and if it is more than 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-sagging effect in high humidity will be reduced. The density of particulate protrusions is 1000 per ^mm2 of surface.
A value of 1,000 or more, more preferably 2,500 or more is appropriate; if it is less than 1,000, the anti-sagging effect in high humidity will be reduced. This density can be determined by observing a minimum of 10 fields of view with a differential interference optical microscope at a magnification of 400 or by first observing 10 fields of view at a magnification of 3000 with a scanning electron microscope. The number is calculated and converted to ^1mm2 . Examples of plastic films include polyester films made of polyethylene terephthalate or its copolymers or mixtures, polyethylene naphthalate or its copolymers or mixtures, etc., polyimide films such as polyesterimide or polyimide, aromatic polyamide films, etc. For example, a polyester film has excellent surface smoothness, and a film with good smoothness in which the size of minute protrusions made of polymerization catalyst residue is several hundred angstroms or less, and a film with excellent surface smoothness as mentioned above. , a surface having uniform fine protrusions in the shape of earthworms, particles, etc., and having a surface roughness of several hundred angstroms or less, etc., are suitable. A method for forming particulate protrusions on these films is, for example, by adding 1 to 50% of an organic solvent containing 10 to 10,000 ppm of water to a dilute solution (10 to 1,000 ppm) of metal alkoxide to hydrolyze the metal alkoxide. A solution in which particles with a particle size of 10 to 500 Å are precipitated and dispersed is prepared, and a resin serving as a binder is added in the solution for 20 to 500 Å.
There is a method of dissolving 5000ppm, applying it on the substrate, and drying it. The metal alkoxide used in the present invention includes:
For example, tetraethoxysilane, aluminum s-butoxide, aluminum t-butoxide,
Aluminum isopropyl borate, trimethylborate, tri-tert-butylborate, tetra-i-propoxytitanium, tetra-n-butoxytitaniumtetrakis(2-ethylhexoxy)titanium, tri-n-butoxytitanium monostearate, tetramethyltitanate, tetraethyl titanate, zirconium tetra-t-butoxide,
Examples of resins used as binders include saturated polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; nylon 6, nylon 66, nylon 610, nylon 11; Single substances and mixtures of various resins such as polyamide such as nylon 12, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, fexino resin, etc. body, or copolymer,
Also, crosslinkable resins such as epoxy resins, urethane resins, silicone resins, and phenolic resins can be used. Examples of ferromagnetic thin films include metal thin films mainly composed of Co, Ni, Fe, etc. formed by oblique or vertical evaporation methods, metal thin films mainly composed of alloys of these, and metals mainly composed of alloys of these. Although thin films (e.g. Co-Cr vertical reinforcement films) can be used,
Oxygen-containing ferromagnetic metal thin film obtained in an atmosphere dominated by oxygen gas during vapor deposition for the purpose of improving the adhesion strength with a plastic film or improving the corrosion resistance and abrasion resistance of the ferromagnetic metal thin film itself. It is preferable to use The oxygen content is at least 3% in atomic ratio relative to the ferromagnetic metal or non-magnetic metal near the surface of the substrate film.
Above, preferably 5% or more is appropriate. Also,
If necessary, it is also possible to form a thin film having a mechanical reinforcing effect, a thin film of an oxide such as Al ₂ O ₃ or SO ₂ , etc. prior to forming the ferromagnetic metal thin film. As mentioned above, the combination of a ferromagnetic metal thin film containing oxygen or a non-magnetic metal layer and particulate protrusions formed thereunder as necessary makes it possible to significantly improve still life. . Note that the still life is also related to the thickness of the ferromagnetic metal thin film, and the thickness
When the thickness becomes less than 400Å, the thickness decreases dramatically.
It is desirable that the thickness be 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 makes it possible to more completely prevent sagging in high humidity environments. The lubricant 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. As a means of doing so,
In addition to coating or vapor-depositing directly on the surface of a ferromagnetic metal thin film, there is also a method of coating or vapor-depositing on the back side of a magnetic recording medium and stacking (winding) the magnetic recording medium.
Sometimes, a method of transferring it to the surface of a ferromagnetic metal thin film is also possible. It is also possible to use a resin binder to firmly bind the lubricant. 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, stearic 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, bentaerythritol tetrastearate, etc. can be used. As the fatty acid amide, caproic acid amide, capric acid amide, lauric acid amide, behenic acid amide, oleic acid amide, linoleic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, etc. can be used. Metal soaps include zinc, lauric acid, myristic acid, valmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, etc.
Salts with lead, nickel, cobalt, iron, aluminum, magnesium, strontium, copper, etc., salts with sulfonic acids such as lauryl, palmityl, myristyl, stearylbehenyl, oleyl, linole, linolenic, etc. and the various metals listed above, etc. can be used. . As the aliphatic alcohol, cetyl alcohol, stearyl alcohol, etc. can be used. As paraffin, n-octadecane, n-
nonadecane, n-tridecane, n-doconane, n
- Saturated hydrocarbons such as dotriacontane can be used. As the silicone, polyquiloxane in which hydrogen is partially substituted with an alkyl group or phenyl group, 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. A void on the front surface, the back surface, or the vicinity thereof of the magnetic recording medium of the present invention, or in the ferromagnetic metal thin film,
Various additives such as rust preventive agents, antistatic agents, antifungal agents, etc. may be present at the interface between the ferromagnetic metal thin film and the plastic film, within the plastic film, etc., as necessary. can. Example 1 On a smooth polyethylene terephthalate biaxially stretched film that has significantly suppressed protrusions caused by polymerization catalyst residue and has a surface roughness of 30 Å or less, the following composition solution was continuously coated and dried to a thickness of about 10 μm. , the surface has particle-like protrusions with a height of about 100 Å with particles composed of hydrolysis products of tetraethoxysilane as the core.
A long film sample having 1 million pieces/mm ² was obtained. Let's call this trial A. Liquid composition Tetraethoxysilane...0.1phr Ethanol...100phr Water...10phr Ethyl acetate...1000phr Polyester (Vylon #200 manufactured by Toyobo Co., Ltd.)
......0.1 phr Example 2 When the liquid composition in Example 1 is changed to the following, approximately 100,000 particulate protrusions with a particle height of approximately 400 Å with the hydrolysis product of aluminum isopropoxide as the nucleus are produced per A sample with mm ² was obtained. This sample is designated as B. Liquid composition Aluminum isopropoxide...0.2 phr Methanol...100 phr Water...20 phr Methyl ethyl ketone...1000 phr Polyester (Vylon #200)...0.1 phr Example 3 If the liquid composition in Example 1 was changed to the following, A sample was obtained which had about 1 million particulate protrusions/mm ² with a particle height of about 50 Å and whose nucleus was a hydrolysis product of tetra-n-butoxytitanium. This sample is C
shall be. Liquid composition Tetra-n-butoxytitanium...0.05phr N-propanol...100phr Water...20phr Ethyl acetate...1000phr Polyester (Vylon #200)...0.1phr Example 4 The liquid composition in Example 1 was as follows. When the sample was changed to , a sample having about 500,000/mm ² particulate protrusions with a particle height of about 300 Å and having the hydrolysis product of tetraisopropyl zirconate as the nucleus was obtained. This sample is designated as D. Liquid composition Tetraisopropyl zirconate...0.1 phr Isopropanol...100 phr Water...10 phr Methyl ethyl ketone...1000 phr Polyester (Vylon #200)...0.1 phr Example 5 From polyethylene terephthalate containing almost no particulates due to polymerization catalyst residue A thin layer of heterogeneous polymer consisting of fine wavy irregularities with a surface roughness of 100 Å is formed by coating and curing a liquid mainly consisting of a modified silicone emulsion containing a thickener on the surface during film formation and stretching. Samples obtained by applying the same coating treatment as in Examples 1 to 4 above using a terephthalate biaxially stretched film as a plastic film were respectively K, L, M,
Let it be N. The particulate resin projections formed on the surfaces of these samples were almost the same as those of the corresponding samples A to D, respectively. Comparative Example 1 The plastic films themselves used in Examples 1 to 4 and Example 5 are referred to as samples S and T, respectively. Each of the above samples A to T was sequentially connected and a Co, Ni ferromagnetic metal thin film (Ni = 20 wt%, film thickness 1000 Å) was formed on each surface by continuous vacuum oblique evaporation method in the presence of a trace amount of oxygen. . The oxygen content of the magnetic layer was 5% in terms of atomic ratio to the metal. After that, each sample is coated with various lubricant solutions on its surface and slit into a predetermined width to make magnetic tape.
Using a prototype video recorder in a RH environment, we measured the state of whirring in the rotating head cylinder, the envelope, and the still life. As a comparative example, sample T 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.
100,000 pieces/mm ² ) was coated with a lubricant solution and then made into magnetic tape, and the above A
The above measurements were also carried out on specific samples of ~T that were made into magnetic tapes without applying a lubricant solution after vapor deposition. These results are shown in the table below.

[Table] Comparative Example 2 A comparison was made between the following conventional example and the embodiment of the present invention. First, JP-A-52-18770, JP-A-52-18770,
The methods described in JP-A No. 84264, JP-A-56-16937, etc. all have a method of roughening the surface shape relatively finely and uniformly, for example, forming wrinkle-like protrusions, worm-like protrusions, etc. However, when compared with the embodiments of the present invention, (a) the shape of the protrusion, especially the spread of the protrusion in the running direction of the head, is approximately 50% of the height. ~100 times blowing,
The slope of the protrusion is very gentle. (b) There is no lubricant. There is a difference. So these things are 30
The drawback is that the cylinder part of the rotating head tends to crack under high temperature and high humidity conditions such as ℃ and 80-90% RH. In addition, the product described in (Japanese Unexamined Patent Publication No. 53-107314) has fine particles of thermoplastic resin protruding from the surface, and the surface roughness is 0.03 to 0.5μ at the maximum height.
A magnetic thin film is formed on biaxially stretched aromatic polyester, and when compared with the examples of the present invention, (a) the material of the particles is different. (b) There is no limit to the spread of the protrusion shape, but since particles are contained in the film, the spread of the protrusion is estimated to be more than 20 times the height. (c) There is no lubricant. There is a difference. Therefore, in a running test at room temperature and humidity, a stick slip occurs when Rmax<0.03μ. Effects of the Invention As is clear from the above examples, the magnetic recording medium of the present invention does not generate sloshing even in high humidity, has a good envelope, and exhibits stable running performance. Furthermore, the still life in high humidity conditions is good, and its practical value is extremely high.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing magnetic recording media in embodiments of the present invention. 1...Plastic film, 2...Nucle of fine particles, 3...Binding resin, 4...Ferromagnetic metal thin film, 5
...Lubricant.

Claims (1)

[Claims] 1. Particles whose core is a fine particle made of a metal alkoxide hydrolysis product obtained by adding 1 to 50% of an organic solvent containing water at a concentration of 10 to 10,000 ppm to a dilute metal alkoxide solution with a concentration of 10 to 1,000 ppm, and whose core is a resin as a binder. 1000 grain-like projections with a height of 30 to 500 Å and a spread of grain-like projections of 1 to 20 times the height.
1. A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on the surface of a plastic film, and a lubricant is present thereon at ^{an amount of 0.5 to 500 mg/m 2 .}