JPS5948825A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is improved of squeaking, etc. in high humidity by forming an undercoating layer having projections within the height range of the specific particles contg. fine particles of SiO2 as nuclei at a specific density on a plastic film substrate and forming a thin ferromagnetic metallic film thereon then sticking a lubricant thereon. CONSTITUTION:A coating liquid prepd. by dissolving 20-10,000ppm a binder resin in a colloidal soln. of silica dispersed with 10-10,000ppm fine particles 2 of SiO2 having 10-500Angstrom particle sizes is coated on a plastic film substrate 1 and is dried, whereby an undercoating layer having projections of 30-500Angstrom particle height in the resin 3 (13) at >=1,000 pieces/mm.<2> is formed. A thin ferromagnetic metallic layer 4 is deposited by evaporation on the undercoating layer, and a lubricant layer 5 or a lubricant stuck layer 15 of stearic amide, stearic glycceride or the like is provided on the layer 4. The squeaking in high humidity is thus eliminated and the magnetic recording medium which has a long still life and excellent travelability and is adaptable to a disc and tape for VTRs, etc. is obtd.

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 them as main components, or thin films of their oxides are deposited by vacuum evaporation,
Ferromagnetic thin film magnetic recording media formed on substrates made of polymer films such as polyester films, polyimide films, non-magnetic metal thin plates, etc. using vacuum film forming methods such as sputtering and ion blasting are conventional coating-type magnetic recording media. It is possible to dramatically improve the recording density compared to magnetic recording media, but in order to increase the density, it is necessary to reduce the gap of the magnetic head and smooth the surface of the magnetic recording medium. At the very least, it is necessary to reduce the spacing loss as much as possible. However, if the surface is too flattened,
Since it causes problems in head touch and running performance, it is necessary to solve this problem by controlling the fine shape of the surface. Ferromagnetic thin Q@iTr! 1. Since the surface orientation of ffFJ magnetic recording media is very small, with a magnetic layer thickness of about 0.01 to 0.6 μm, it depends to a large extent on the surface shape of the Plus Deck film that is the substrate. It has been proposed that the surface circle of l is 1'/, I L = tech. An example of this is JP-A-52-18″r70 Publication No. 4
jlJ, 411' Publication No. 52-84264, JP 11i' (Publication No. 54408 Tei No. 3, !1Ken111Sho5)
Publication No. 3-116115, JP 53-12868
5 Bow Publication, JP-A-54-94574, j(1+, JP-A-66-10.456, JP-A-56-1693)
It is described in the 7th long bulletin, etc. In all of these examples, the head touch and running properties are improved by roughening the surface shape relatively finely and uniformly, for example, by eliminating the formation of wrinkle-like protrusions, or by forming worm-like or granular protrusions. This is an attempt to improve all at once. The surface condition seen in the above example is a head touch at normal temperature and humidity.

It is very effective in terms of head running performance. However, 3
It has a drawback that a part of the cylinder of the rotary head tends to generate noise in high humidity such as 0° C. 8° to 90% R,H. One way to solve this problem is to use a polyester film as a substrate, and when forming a ferromagnetic layer in vacuum, the polyester oligomer contained therein is deposited as fine crystals on the substrate surface, and then the ferromagnetic layer is deposited on the substrate surface. The present inventors have already proposed forming a thin metal film layer, but in this case, the frequency of precipitation of oligomer crystals is largely location dependent, making it difficult to precipitate oligomer crystals evenly distributed over the entire surface. , which tends to cause uneven distribution depending on location. As a result, the envelope characteristics of the resulting magnetic recording medium are disturbed.
Yazui had some flaws.

In addition, 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. 63-107314 has good running properties and good image quality. It is being 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 will be 0.03 μm.
If it is less than m, stick-slip occurs and running performance deteriorates.

Purpose of the Invention The present invention aims to provide a metal thin film magnetic recording medium that improves noise in high humidity environments, improves reproduced image quality, and is suitable for high-density recording. 1000 particle-like protrusions of height 3o~, 6o○ people (
The present invention is characterized in that an undercoat layer having an atomization ratio of 11/A or more is provided, a ferromagnetic metal thin film is formed on the undercoat layer, and a lubricant is further present on the metal thin film.

DESCRIPTION OF THE EMBODIMENTS Figures 1 and 2 show cross sections of embodiments of the magnetic recording medium of the present invention. In the figures, 1 and 11 are plastic plastic films, 2 and 12 are fine particle cores made of silica, and 3. , 13 are binding resins for fixing the cores 2 and 12 to the plastic plate fill 'xl and 11Jl, 4 and 14 are ferromagnetic metal thin films, and 6 and 15 are lubricants. In these figures, the combination of fine particle core 2 and binding resin 3 and the combination of fine particle core 12 and binding resin 13 are the undercoat layer.

In FIG. 1, the lubricant 5 is present on the entire surface of the ferromagnetic metal thin film 4, but in FIG.

The height of the particulate protrusions was measured using a high-precision stylus-type surface roughness measuring device (
TALYSTEP-1, manufactured by TATLOR-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 JIS BO601, Rmax. Then, the height suitable for the present invention is in the range of 30 to 500 people, more preferably 6 to 300 people.

If it is less than 3 o 8, it is difficult to obtain a squeal prevention effect in high humidity.
If the number of participants is 500 or more, disturbances in the envelope are likely to occur.

The planar spread of the particulate protrusions is 1 to 20 times (1!f) 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. do.

The density of particulate protrusions is 1.0 per m and a of the surface.
A value of 00 or more, more preferably 2,600 or more is appropriate, and a value of 1,000 or more reduces the squeal prevention effect in high humidity. This density has a magnification of 4o.

Observe a minimum of 10 fields of view with a differential interference interference optical microscope or a minimum of 10 field of view with a scanning electron microscope at a magnification of 3000, and calculate the number of particulate projections with rT 6: per 1m7 within those fields of view. It was replaced by a leopard.

Plastic films include polyethylene terephthalate or copolymers and mixtures thereof, polyester films made of polyethylene naphthalate and copolymers and mixtures thereof, polyimide films such as polyester-imide and polyimide, and aromatic polyamide films. , etc. Table 1 TjI Excellent smoothness,
For example, a polyester film has good smoothness, contains almost no microprotrusions made of residual polymerization catalyst, or has microprotrusions in the size of several hundred or less, and has a wrinkled or earthworm-like shape as described above. Items with uniform fine protrusions such as granules formed on the surface, and the surface roughness is less than a few inches,
etc. are appropriate. As a method for forming an undercoat layer having particulate projections on these films, for example, silica fine particles having a particle size of 10 to 500 are coated with 10 to 101
There is a method in which 20 to 10,000 ppm of a resin serving as a binder is dissolved in a silica colloid solution containing 0.000 ppm, and then applied onto a plastic film and dried.

The silica fine particles used in the present invention include, for example, 1y! obtained from silicon tetrachloride by a dry method. , Nrika at the end of the costume (
fIJ: Aerosil: Japan T-/”x
Fine powder silica (e.g.
There are silica sol obtained by ion exchange of sodium silicate (e.g. Snowtex: Nissan Chemical Industries @)), etc., and these are mixed in a solution containing mainly water, alcohol, ketone, ester, etc. Disperse it in water and use it after removing coarse particles as necessary. Examples of the 1a/1 resin serving as a binder include fjl full polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, nylon 6, nylon 66, -)-ylon 610. Nylon 11. Polyamide such as nylon 12, polystyrene, polycarbonate.

Polyarylates, polysulfones, polyethersulfones, polyacrylates, polyvinyl chloride.

Single substances, copolymers, and mixtures of various resins such as polyvinyl butyral, polyphenylene oxide resin, and phenoxo resin can be used, and epoxy resins,
Crosslinkable resins such as urethane resins, silicone resins, phenolic resins, melamine resins, or modified resins thereof can also be used.

Examples of ferromagnetic metal thin films include metal thin films mainly made of Co, Ni, Fe, etc. formed by oblique or vertical vapor deposition, and metal thin films mainly made of alloys thereof (
For example, Go-Or perpendicular magnetization film) can be used, but it is necessary to improve the adhesion strength with the plastic film or to improve the corrosion resistance of the ferromagnetic metal thin film itself.

For the purpose of improving wear resistance, it is desirable to use a ferromagnetic metal thin film containing oxygen obtained by changing the atmosphere during vapor deposition to an atmosphere in which oxygen gas is dominant.

The appropriate oxygen content is at least a factor of 3 or more, preferably 6% or more, in terms of atomic ratio to the ferromagnetic metal or non-magnetic metal near the surface of the substrate film. Also,
If necessary, prior to forming the ferromagnetic metal thin film, it is also possible to form a thin film with a mechanical reinforcing effect, such as an oxygen-containing metal thin film such as Ti, Or, or Ni, or an oxide thin film such as Al2O5゜5i02. It is.

A ferromagnetic metal thin film containing oxygen as described above, or the above nonmagnetic metal layer formed thereunder as necessary;
In combination with a base layer having particulate protrusions, it is possible to significantly improve still life. Note that the still life is also related to the thickness of the ferromagnetic metal thin film, and since the still life rapidly decreases when the thickness is less than 400 Å, it is desirable that the thickness is 400 Å or more.

By allowing a lubricant to exist on the surface of the ferromagnetic metal thin film layer, it is possible to further enhance the running performance improvement effect based on the shape of the particulate protrusions. This makes the prevention of squealing in high humidity even more complete.

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. In addition to applying it directly to the surface of the ferromagnetic metal thin film or vapor-depositing it, other methods include coating it on the back side of the magnetic recording medium, or depositing it on the back side of the magnetic recording medium, and then transferring it to the surface of the ferromagnetic metal thin film when stacking (winding) the magnetic recording medium. urge)
The 5th method is also 1st power. It is also possible to use a resin binder or the like to firmly adhere the lubricant.

As the lubricant, fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, halaffins, silicones, fluorine surfactants, inorganic lubricants, etc. can be used.

In the presence of lubricant, 0.5 to 500 m per surface
g, more preferably 5 to 200 mg.

Fatty acids include 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, stearic acid monoglyceride, palmitic acid monoglyceride, oleic acid monoglyceride, pentaerythritortetrastearate, etc. can be used.

Examples of fatty acid amides include caproic acid amide, capric acid amide, lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

Oleic acid amide, linoleic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, etc. can be used.

Metal soaps include zinc and lead such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, and linuric acid.

For fE, salts with nickel, cobal l-, iron, aluminum, macnesium, strontium, copper 2, etc., salts with sulfonic acids such as lauryl, palmityl, myristyl, stearylbehenyl, oleyl, linole, linole, etc. and the various metals listed above are used for fE. Among the aliphatic alcohols that can be used, cetyl alcohol, stearyl alcohol, etc. can be used.

As the paraffin, saturated hydrocarbons such as n-octadecane, n-nonadecane+n-tridecane, n-tocorin, and n-todoriaconcune can be used.

As the silicone, poly/lochileaf resins in which hydrogen is partially substituted with an alkyl group or a phenyl group, and those modified with fatty acids, aliphatic alcohols, acid-ramide, etc. can be used.

Fluorine-based surfactants include perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonic acids, sodium, potassium, magnesium, zinc, aluminum, iron, cobalt, nickel, etc., half-0-roalkyl phosphate esters, and perfluoroalkyl phosphates. Betaine, perfluoroalkyltrimethylammonium salt, perfluoroethylene oxite, per70roalkyl fatty acid ester, etc. can be used.

Inorganic lubricants include graphite powder, molybdenum disulfide powder, tungsten disulfide powder, molybdenum selenide powder, and tungsten selenide powder.

Examples include carunium fluoride powder.

Various additives such as an antistatic agent and an antifungal agent 2 can be present on the front surface, the back surface, or the surface of the magnetic recording medium of the present invention, if necessary.

Example 1 The following composition solution was applied continuously to a smooth polyethylene terephthalate film L having a surface roughness of 30 F or more by significantly suppressing protrusions caused by residual polymerization catalyst to a thickness of about 1 μm. After coating and drying, a long film sample was obtained on which a coating layer was formed and had particle-like protrusions of about 100 people in height with silica fine particles as cores on the surface of about 6,000,000 4A. This sample is designated as A.

〆Night Composition Snowtex・0・・・・・・・・・2
phr (manufactured by +1 San Kagaku Kogyo Hina) Methanol ゛"""' 200 phr Ethyl acetate ...... s o o ph
r Example 2 By changing the liquid composition in Example 1 to the following, particulate protrusions with a height of about 80 mm using silica fine particles as cores were formed by about 1 million ttu7. A long film sample was obtained with one coat of undercoat having ,H. This sample is designated as B.

Liquid composition toluene ・・・・・・・・・ 100
phr methyl ethyl ketone ・・・・・・・・・
・300 phr polyether sulfone...
...0.2phr T-〇: Ro-4) Example 3 By changing the liquid composition to the following in Example 1, particles with a height of about 200 with silica fine particles as the core were formed. A long film sample was obtained in which a toe coating layer having approximately 200,000 protrusions/- was formed. This sample is designated as C.

Liquid composition Ethyl acetate 1000Ph
rToluene ・・・・・・・・・100
phr hollyester...0.
6phr Example 4 By changing the liquid composition to the following in Example 1, a long film sample was formed with an undercoat layer having about 500,041 J of particulate protrusions with a height of about 250 and silica fine particles as cores. 71 suda. This sample is designated as D.

Liquid composition Aerosil"972 -=1.-0.0.
1 phr acetone...50
0 phr ethyl acetate...40
0 phr toluene 10
Ophr Example 6 A liquid mainly consisting of a modified silicone emulsion containing a thickener was applied and cured during film formation and stretching on the N-face, which was made of polyethylene terephthalate with almost no particulates due to residual polymerization catalyst. Using a polyester biaxially stretched film on which a thin layer of different types of polymer consisting of fine wavy irregularities with a surface roughness of 100 μm was formed, the same coating treatment as in Examples 1 to 4 was applied to form a base layer. Let L, M, and N be the ``Saseda trial rate,'' respectively. The particulate protrusions 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 used in Examples 1 to 4 and Example 5 were used as samples S and T, respectively.

shall be.

The above A-T samples were sequentially connected and a CoNi ferromagnetic metal thin film (Ni =
20 W j% + film thickness 1000 people) was formed in the presence of a small amount of oxygen. The oxygen content of the magnetic layer was 6 times the atomic ratio to the metal. After that, a lubricant solution of each weight was applied to the surface of each sample, and magnetic tape was made by slitting it to a predetermined width.The tape was hung on a prototype video recorder in an environment of 30°C, 90% R8H, and a part of the rotating head cylinder was used. The state of the sound, envelope, and still life were measured. As a comparative example, sample T was heat-treated before vapor deposition to precipitate polyester oligomer crystals on the surface, and then the four columns were vapor-deposited to form microprotrusions (approximately 300 in height) made of oligomer crystals. , density of about 1oJ511 sea) was coated with a lubricant solution, and then magnetic tape was formed, and the above A and T
Regarding a specific sample 7L1, which was made into a magnetic tape without applying a lubricant solution after vapor deposition, the following measurements were also carried out. These results are shown in the table below.

(Hereinafter F margin) Effects of the Invention As is clear from the above examples, the magnetic recording medium of the present invention does not generate squeal even in high humidity, has good bending/velope, and has stable running performance. shows. Furthermore, the methyl lifespan in high humidity conditions is also good, and both practical values are extremely high.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a magnetic recording medium according to another embodiment of the present invention. ...Plastic fill 'E'-'2.
12...Nucle of fine particles, 3,13...1
Ri・1 fat, 4.14...Ferromagnetic thin film, E5',
15...Lubricant.

Claims (1)

[Claims] An undercoat P layer having particle heights of 30 to 500 cm or more with silica fine particles as cores and resin as a binder is provided on the plastic film substrate surface, and a ferromagnetic metal thin film is provided on the undercoat layer. 1. A magnetic recording medium characterized in that a lubricant is present on the metal thin film as described above.