JPS5942637A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin metallic film type magnetic recording medium causing hardly squeaking at high humidity and suitable for use in high density recording by allowing a lubricant to exist on a ferromagnetic thin metallic film formed on the surface of a plastic film consisting of fine particles of the hydrolyzate of metallic alkoxide as nuclei and resin as a binder for controlling the uneven surface state. CONSTITUTION:A ferromagnetic thin metallic film is formed on the surface of a plastic film, and a lubricant is allowed to exist on the thin film. The plastic film consists of fine particles of the hydrolyzate of metallic alkoxide as nuclei and resin as a binder, and it has >=1,000 particle-shaped protrusions of 30-500Angstrom height per 1mm.<2> of the surface. For example, an org. solvent contg. water is added to a dil. soln. of metallic alkoxide to hydrolyze the alkoxide and to deposit and disperse particles of 10-500Angstrom particle size in the soln. After dissolving resin as a binder in the soln., the soln. is applied to a substrate and dried to form said plastic film. A thin metallic film contg. Co, Ni, Fe or an alloy thereof as the principal component is used as said ferromagnetic thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

The 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 blasting. 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. However, in order to achieve this high density, 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 made too flat, head touch and running performance will be affected, 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 between 0.01 and 0.
．． Since it is very small at about 5 μm, 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. Examples are JP-A-62-18770, JP-A-52-84264, and JP-A-54-4.
0883, JP 53-116115, JP 53128686, JP 54-94574
No. 10465, JP 56-10465, JP 56-10465
16937, etc.

In all of these examples, the head touch is achieved by roughening the surface shape relatively finely and uniformly, for example, by forming wrinkle-like protrusions.

This is an attempt to improve running performance all at once. The surface condition shown in the above example is very effective in terms of head touch and head running performance at room temperature and humidity.

However, it has the disadvantage that a part of the cylinder of the rotary head tends to generate noise at high temperatures such as 30°C and 80 to 9o% R,H. One way to solve this problem is to use a polyester film as a substrate, and when forming a ferromagnetic layer in a vacuum, the polyester oligomer contained in the film is precipitated as fine crystals on the surface of the substrate. A proposal has been made to form a magnetic metal thin film layer, but in this case, the frequency of precipitation of oligomer crystals is highly dependent on location, making it difficult to evenly distribute the oligomer crystals over the entire surface, resulting in uneven distribution depending on location. tends to occur. Therefore, there is a drawback that the envelope characteristics of the obtained magnetic recording medium are 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-53-107314 has good running properties and good image quality. ing. However, in this case, even if an attempt is made 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.
m or less, stick-slip occurs and running performance deteriorates.

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 improves noise in high humidity environments and improves both image quality.

Structure of the Invention The magnetic recording medium according to the present invention has particle-like constrictions of 100 to 500 particles in height of 30 to 500 particles each having a core of fine particles made of a hydrolysis product of a metal alkoxide and a resin as a binder.
i A magnetic recording medium according to the present invention is characterized in that a ferromagnetic metal thin film is formed on the surface of the plastic film and a lubricant is present thereon. This figure shows a cross section of the embodiment, in which 1 and 1' are plastic films, 2,2' are cores of fine particles made of a hydrolysis product of metal alkoxide, and 3 and 3' are cores 2 and 2' of plastic. a binding resin for fixing onto the films 1 and 1';
4 and 4' are ferromagnetic metal thin films, and 5.5' is a lubricant. 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 6' is present 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, manufactured by TAYLOR-HOBSON), and is expressed as the distance from the top of the unevenness to the bottom of the valley according to the maximum surface roughness specified in JISBO601, Rmax. The height suitable for the invention is in the range of 30-600 people, more preferably 50-308. If it is less than 308 Å, it is difficult to obtain the effect of preventing squealing in high humidity, and if it is more than 600 Å, the envelope is likely to be disturbed.

The planar spread of the particulate protrusions 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 appropriate density of the particulate protrusions is 1,000 or more, more preferably 2,500 or more per surface 11.
If it is less than 10oO, the squeal prevention 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 with a magnification of 400, or with a scanning electron microscope with a magnification of 30.
At 00, first observe 107 Higashino, and calculate the number of particulate resin protrusions existing within the field of view and calculate the number of 1 myrb 2 equivalents.
This is the IF-conversion '141 Lit model.

Examples of plastic films include polyester films made of polyethylene terephthalate or its copolymers or mixtures, polyethylene naphthalate or its copolymers or mixtures, polyimide films such as polyesterimide or polyimide, and aromatic films. polyamide films, etc., which have particularly excellent surface smoothness; taking polyester films as an example, films with good smoothness in which the size of microprotrusions made of polymerization catalyst residues are several hundred angstroms or less. Suitable materials include those on which uniform fine protrusions such as those described above in the form of wrinkles, earthworms, or grains are formed on the surface and whose surface roughness is several hundred Å or less. As a method for forming particulate protrusions on these films, for example, 1 to 5% of an organic solvent containing 10 to 10,000 ppm of water is added to a dilute solution of metal alkoxide (IC) (1,000 ppm).
Add 0% and hydrolyze the metal alkoxide to reduce the particle size to 10%.
There is a method in which ~500 particles are precipitated and dispersed to form a ζ solution, in which 20 to 5000 ppm of resin as a binder is dissolved, and then applied onto a substrate and dried.

Examples of the metal alkoxide used in the present invention include tetraethoxysilane, aluminum t-butoxide, and aluminum t-butoxide.

Aluminum isopropyl borate, trimethylborate, tri-tert-butylborate, tetra-1-propoxyhene, tetra-n-butoxytitaniumtetrakis(2.ethylhexoxy)titanium.

tri-n-butoxytitanium monostearate, tetramethyl titanate, tetraethyl titanate.

Zirconium tetra-t-butoxide, tetraisopropyl zirconate, indium inpropoxide, etc., and binder resins include saturated polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, nylon 6, nylon 66, etc. , polyamides such as nylon 6101, nylon 11, and nylon 12, polystyronopebolycarbonate, polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, phenoxy 7 resin, etc. A single substance, a mixture, or a copolymer of various resins can be used, and crosslinked AH resins such as epoxy resins, urethane resins, silicone resins, and phenol resins can also be used.

Examples of the ferromagnetic thin film 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. Thin films (for example, Co-Cr vertically reinforced films) can be used, but the atmosphere during vapor deposition is changed to oxygen gas to improve the adhesion strength with plastic films. It is desirable to use a ferromagnetic metal thin film containing oxygen obtained in an atmosphere where 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 substrate film. In addition, if necessary, a thin film with a mechanical reinforcing effect, 82°
3. It is also possible to form a thin film of oxide such as SO2.

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 methyl lifetime 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. As a result, the prevention of squealing in high humidity becomes more complete.O The lubricant on the ferromagnetic metal thin film may be present on the entire surface as shown in Figure 1, but as shown in Figure 2. It may be made to exist locally. 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 to firmly bind the lubricant.

Examples of lubricants that can be used include fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, surfactants, silicones, fluorine surfactants, and inorganic lubricants. 0.6-600 per hit
(2), more preferably 6 to 200 (2).

Fatty acids include 1, lauric acid, and myristic acid.

palmitic acid, stearic acid, behenic acid, oleic acid,
Those having 12 or more carbon atoms such as linoleic acid and linoleic acid can be used.

As the fatty acid ester, ethyl stearate, butyl stearate, amyl stearate, stearate, monoglyceride arinate, monoglyceride noclumitate, monoglyceride oleate, pentaerythritol) lastearate, 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 and lead such as lauric acid, myristic acid, balmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linuric acid.

Salts with nickel, cobalt, iron, aluminum, magnesium, strontium, copper, etc., salts with sulfonic acids such as lauryl, harmityl, myristyl, stearylbehenyl, oleyl, linonoperilne, etc., and the various metals mentioned above, and the like can be used. As the aliphatic alcohol, cetyl alcohol, stearyl alcohol, etc. can be used.

As the paraffin, saturated hydrocarbons such as n-octadecane, n-nonadecane, n-)lysocane, n-doconane, and n-todriacontane can be used.As the silicone, hydrogen is partially substituted with an alkyl group or a phenyl group. polysiloxane and these,
Those modified with fatty acids, aliphatic alcohols, acid amides, etc. can be used.

Examples of fluorosurfactants include perfluoroalkyl carboxylic acids and perfluoroalkyl sulfonic acids, tono salts such as sodium, potassium, magnesium, zinc, aluminum, iron, cobalt, and nickel, barfluoroalkyl phosphate esters, and perfluoroalkyl betaines. , perfluoroalkyltrimethylammonium salt, barfluoroethylene 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, aged calcium fluoride powder, and the like.

A rust preventive agent is applied to the front surface, back surface, or the vicinity thereof of the magnetic recording medium of the present invention, the void in the ferromagnetic metal thin film, the interface between the ferromagnetic metal thin film and the plastic film, the inside of the plastic film, etc. by known means.

Various additives such as antistatic agents and anti-oxidant agents may be present as necessary.

Example 1 The following composition solution was coated on a smooth polyethylene terephthalate biaxially stretched film that had significantly suppressed protrusions caused by residual polymerization catalyst and had a surface roughness of 308 or less, and was continuously coated and dried to a thickness of 10 μm. , about 100 mm in height with a core of particles consisting of a hydrolysis product of tetraethoxysilane on the surface.
A long film sample having about 1 million particulate protrusions/word 2 was obtained. This sample is designated as A.

Liquid composition Tetraethoxysilane -... Conflict... 0.1 ph
rEthanol φ・0・・100ph
r water e...
10 phr ethyl acetate e...bottle...1
000 phr polyester -”**@0
．． 1 phr Example 2 When the liquid composition in Example 1 was changed to the following,
A sample was obtained which had about 100,000 particle-like protrusions/word2 with a particle height of about 40 mm and having a core of a hydrolysis product of aluminum isopropoxide. This sample is designated as B.

Liquid composition Aluminum isopropoxide・Φ・・・・・ 0, 2
phr methanol *@e4@100
phr water asses
s 2Q phr methyl ethyl ketone
...1000 phr polyester (Byron #2o
O)... 0.1 phr Example 3 When the liquid composition in Example 1 was changed to the following, the particle height was about 60 people with the hydrolysis product of tetra-n-butoxytitanium as the core. A sample having approximately 1,000,000 particle-like protrusions per square inch was obtained. This sample is designated as C.

Liquid composition Tetra-Kanobutoxytitanium ・・・・・・ 0.05
phrn-globanol@11@@@11100
phr water *easaa
20 phr ethyl acetate・1111・・1110
0ophr polyester (by Oy #2oo) e@se
s o, 1 phr Example 4 When the liquid composition in Example 1 was changed to the following,
Approximately 500,000 particle protrusions/B with a particle height of approximately 300 with the hydrolysis product of tetrainpropyl zirconate as the core
Two samples were obtained. This sample is designated as D.

Liquid composition Tetraisopropyl zirconate...0.1ph
risopropatool...@bone・100p
hr water 9...
10phr Methyl ethyl ketone・・・・・・-1
000phr polyester (Pyro 7 #200) ---
--0.1 phr Example 6 Made of polyethylene terephthalate that contains almost no particulates due to residual polymerization catalyst, a liquid mainly consisting of a modified silicone emulsion containing a thickener is applied and cured on the surface during film formation and stretching. The same coating treatment as in Examples 1 to 4 above was applied using a polyethylene telegraph film on which a thin layer of different polymers consisting of fine wavy irregularities with a surface roughness of 100 mm was formed using a biaxially stretched film as a plastic film. The samples obtained were labeled K and L, respectively.

Let them be M and N. The particulate resin protrusions formed on the surfaces of these samples correspond to those of A to D. Effects of the Invention As is clear from the above examples, the magnetic recording medium of the present invention has no noise even in high humidity. It does not generate any noise, 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 the drawing]

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

Claims (1)

[Claims] A ferromagnetic metal is applied onto the surface of a plastic film on which more than 1,000 particulate protrusions with a particle height of 30 to 500 are present on the surface, each having a particle height of 30 to 500 and having fine particles made of a hydrolysis product of a metal alkoxide as a core and a resin as a binder. A magnetic recording medium characterized by forming a thin film and having a lubricant present on the thin film.