JPS5992427A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve tape squealing occurring in high humidity and reproduction of image quality by forming a thin ferromagnetic metallic layer and a lubricant layer on an undercoat having granular protuberances composed of microgel particles made of cross-linked polymer as nuclei and having certain particle height, formed on a plastic film base. CONSTITUTION:The nuclei 2 themselves form granular resin protuberances and adhere to a plastic film base 1. A lubricant layer 5 coats all the surface of a thin ferromagnetic metallic layer 4. The height of granular resin protuberances is 3-50nm measured with a tracer method type surface roughness meter. It is suitable that the planar extension of the protuberances is 1-20 times the height of them. The plastic film base is made of polyester of polyethylene terephthalate or its copolymer, or the like. The microgel particles made of cross-linked polymer is obtained, for example, by using a monomer having >=2 unsatd. double bonds as an essential material and emulsion polymerizing it, and it is suitable that its particle diameter is <=200nm.

Description

[Detailed description of the invention] Industrial applications Magnetic recording media such as magnetic tape and magnetic disks.

Conventional structure and its problems Vacuum vaporization of iron, cobalt, nickel, alloys containing these as main components, or thin films of their oxides
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 blating can be produced using conventional coating methods. It is possible to dramatically improve the recording density compared to conventional magnetic recording media, but in order to achieve this high density, the gap of the magnetic head must be made smaller and the surface of the magnetic recording medium must be made smoother. It is necessary to reduce the amount of nuvecin cross as much as possible. However, if you flatten the surface too much,
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. The surface properties of ferromagnetic thin film magnetic recording media are such that the magnetic layer thickness is 0.0.
Since it is very small, about 1 to 0.6 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-52-18770, JP-A-52-84264, and JP-A-54-4.
0883, JP 53-116115, JP 63-128685, JP 54-9457
Publication No. 4, 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, it causes wrinkle-like protrusions to form,
By forming earthworm-like or granular protrusions, head touch and running performance are improved 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, it has the disadvantage that a part of the cylinder of the rotary head tends to generate noise in high humidity of 3Q'080 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 precipitated as fine crystals on the surface of the substrate. The present inventors have already proposed forming a ferromagnetic metal film layer, but in this case,
The frequency of precipitation of oligomer crystals is highly dependent on location, making it difficult to evenly distribute and precipitate oligomer crystals over the entire surface, which tends to cause uneven distribution depending on location.

Therefore, there is a drawback that the envelope characteristics of the resulting magnetic recording medium are likely to be disturbed.

Further, it is known that a polyester film having thermoplastic fine particles protruding from its surface as described in JP-A-53-107314 has good running properties and good image quality. However, in this case, even if an attempt is made to improve the surface properties of the magnetic recording medium in order to increase the recording density, the surface roughness remains o. If the thickness is less than 0.03 μm, nucleation occurs and the runnability becomes poor.

OBJECTS OF THE INVENTION The present invention aims to provide a metal thin film magnetic recording medium which is suitable for high-density recording and has improved noise in high humidity environments and improved reproduced image quality.

Structure of the Invention The present invention provides particle-like resin protrusions of 1000 to 30 to 500 in height with microgel particles made of crosslinked polymer as the core.
It is characterized by forming a ferromagnetic metal thin film on the surface of a plastic film provided with an undercoat layer having a particle size/l, I12 or more, and having a lubricant present thereon. This problem is solved by the synergistic effect of the shape of the surface of the magnetic layer and the lubricant present therein.

DESCRIPTION OF EMBODIMENTS FIGS. 1 and 2 show a cross section of an embodiment of the magnetic recording medium of the present invention. 3' is a binding resin for fixing the core 2' to the plastic film substrate 1'; 4 and 4' are ferromagnetic metal thin films; 5;

5' is a lubricant. In FIG. 1, the core 2 itself forms particulate resin protrusions and is fixed to the plastic film substrate 11 by itself, and in FIG. 2, the core 2'
Particulate protrusions are formed from the bonding resin 31 and the bonding resin 31. Although the lubricant 5 still exists on the entire surface of the ferromagnetic metal thin film 4, the lubricant 5' exists only in a specific portion on the ferromagnetic metal thin film 4'. In these figures, the combination of cores 2 and 2' and resin 3' is the undercoat layer.

The height of the particulate resin projections was measured using a high-precision stylus-type surface roughness measuring device (TALYSTEP-1, TATLOR-HOB).
Measured by JIS-BO60 (manufactured by SON).
According to RNL, the maximum value of surface roughness specified in 1.1 is expressed as the distance from the top of the unevenness to the bottom of the valley, and the height suitable for the present invention is 30 to 500. If it is less than 3 o 8, it is difficult to obtain the effect of preventing squealing in high humidity, and SOO
Above Å, the envelope tends to be disturbed.

The planar extent of the particulate resin protrusions is suitably 1 to 2 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 resin protrusions is 100 per 2 parts of the surface.
A value of 0 or more, more preferably 2,500 or more is appropriate, and if it is less than 1,000, the squeal prevention effect in high humidity will be reduced. This density can be determined by observing a minimum of 1o field of view with a differential interference optical microscope with a magnification of 400 or, currently, with a scanning electron microscope with a minimum of 10 fields of view with a magnification of 3000. The number is calculated and converted to 1 to 2.

Plastic films used for the substrate include polyethylene terephthalate (polyethylene terephthalate) or copolymers and mixtures thereof;
Polyester films made of polyethylene naphthalate or its copolymers, mixtures 2, etc., polyimide films such as polyester imide, polyimide, aromatic polyamide films, etc., which have particularly excellent surface smoothness, and polyester films. Examples include those with good smoothness that contain almost no microprotrusions made of polymerization catalyst residual aroma, or with the size of microprotrusions of several hundred angstroms or less, and those with the aforementioned wrinkle-like or earthworm-like two-grain shape. A material with uniform fine protrusions formed on the surface and a surface roughness of several hundred angstroms or less is suitable.

Microgel particles made of cross-linked polymers are obtained by emulsion polymerization using, for example, as a main raw material a chemical compound (polyfunctional polymer) having two or more unsaturated double bonds, and the particle size Appropriately, the number of participants is 2,000 or less, preferably 50 to 1,000. Examples of polyfunctional monomers include divinylbenzene, ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate rylate, methylene bisacrylamide, trimethylolpropane triacrylate, and tetramethylo-! There are remethane tetraacrylate, etc., and examples of additives added to these polyfunctional additives as necessary include nutylene and acrylic acid.

Methacrylic acid, itaconic acid, allyl acrylate.

Allyl methacrylate, acrylamide, methacrylamide, acrylonitrile, vinyl acetate.

Examples include vinyl chloride. Add an emulsifier such as sodium dodecyl sulfate to the above emulsifier, and add 2S208/N.
Add a reaction initiator such as aHCO3 to a concentration of about 1
A dispersion of microgel particles is obtained by carrying out a reaction in a 0% aqueous dispersion system at 60° C. for 10 to 30 hours, and then removing inorganic salts by dialysis.

This solution is diluted with alcohol, coated on a plastic film, and dried to form the undercoat layer shown in Figure 1.

In addition, in the case of the structure of the undercoat layer as illustrated in Fig. 2, a binder selected from various thermoplastic resins, crosslinkable resins, etc. is added to the above diluted microgel solution and then applied onto the plastic film. Apply and dry (cure).

Examples of the ferromagnetic metal thin film include metal thin films mainly made of Go, Ni, Fe, etc., formed by oblique evaporation or vertical evaporation, 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, which is obtained when the atmosphere during vapor deposition is dominated by oxygen gas.

The oxygen content is at least 3 in atomic ratio to the ferromagnetic metal or non-magnetic metal near the surface of the substrate film.
% or more, preferably 5% or more. Furthermore, if necessary, prior to forming the ferromagnetic metal thin film, a thin film having a mechanical reinforcing effect, for example, an oxygen-containing metal thin film such as Ti, Or, Ni, etc., At203.

It is also possible to form a thin oxide film such as Si 2 O, etc.

The combination of the above-mentioned ferromagnetic metal thin film containing oxygen, or the above-mentioned non-magnetic metal layer formed thereunder as necessary, and the underlayer having particulate protrusions, can significantly improve the methyl lifespan. It is possible to improve the Note that the still life is also related to the thickness of the ferromagnetic metal thin film, and since the methyl 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 further ensures complete prevention of squealing 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. 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 fix 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.

The amount of lubricant present is 0.6 to 500 per m2 of surface.
ml, more preferably 6 to 2 ml.

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.

The fatty acid ester is ethyl stearate/L/.

Butyl stearate, amyl stearate, stearic acid monoglyceride, palmitic acid monoglyceride, oleic acid monoglyceride, pentaerythritol tetrastearate, 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 bisstearic acid amide, ethylene binunutearic acid amide, etc. can be used.

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

Salts with nickel, cobalt, iron, aluminum, magnesium, strontium, copper 2, etc., salts of nurphonic acid such as lauryl, palmityl, millinutyl, nutearyl, behenyl, oleyl, linole, rinne, etc. and the various metals listed above, and the like can be used.

Aliphatic alcohols such as cetyl alcohol and stearyl alcohol can be used.

As the paraffin, saturated hydrogen such as n-oftadecane, n-nonadecane, n-)lysocane, n-tocosan, and n-todriacontane can be used.

As silicones, polysiloxanes in which hydrogen is partially substituted with alkylphenyl groups, and those modified with fatty acids, fatty acid alcohols, etc. can be used.

Examples of fluorine-based surfactants include NOGU fluoroalkyl betaaic acid and perfluoroalkyl carbon lead, A! Reminium, iron, metal salts, nickel salts, perfluoroalkyl phosphate esters, fluoroalkyl betaine, fluoroalkyl! Rekyltrimethylammonium salt, fluoroethylene oxide, perfluoroalkyl fatty acid ester, etc. can be used.

Examples of the inorganic lubricant include graphite powder, binary molybdenum powder, tungsten disulfide powder, molybdenum selenide powder, tannin powder, calcium fluoride powder, and the like.

A rust preventive agent is applied to the front surface, the back surface of the magnetic recording medium of the present invention, or in the vicinity thereof, a gap in the ferromagnetic metal thin film, an interface between the magnetic metal thin film and the plastic film substrate, and the inside of the plastic film substrate by known means. Various additives such as inhibitors and antibacterial agents may be present as necessary.

Next, a more specific example will be explained.

Example 1 The following composition solution was applied on a smooth polyethylene terephthalate biaxially stretched film that had significantly suppressed protrusions caused by residual polymerization catalyst and had a surface roughness of 30 Å or less. 9 Continuously coated to a thickness of about 10 μm and dried. As a result, about 30 particulate protrusions with a height of about 150 people with microgel particles as the core are formed on the surface.
A long film sample having 10,000 pieces/piece was obtained. Let this sample be a person.

Liquid composition: divinylbenzene:nutylene (4:1) copolymer microgel particles (average particle size: 200 people; particle size is the value obtained by scanning electron microscopy)
...0. 0 5 phr Sodium Dodecyl Sulfate
・・・・・・・・・・・・・・・ Trace amount of water
・・・・・・・・・・・・・・・1op
hr, alcohol...
・・・・・・・・・ 1000 phr Example 2 If the liquid phase composition in Example 1 is changed to the following,
Approximately 600,000 particulate protrusions with a height of approximately 300 people/1. A long film sample having I and 2 was obtained. This sample is designated as B.

Liquid composition Trimethylolpropane triacrylate: methyl methacrylate (1:1) copolymerized microgel particles (average particle size 4008) ・・・・・・・・・・・・・・・ 0.1 phr Sodium dodecyl sulfate ・・・・・・・・・・・・・・・ slight
Quantity of water・・・・・・・・・・・・
...2 phr methyl ethyl ketone
・・・・・・・・・・・・・・・1000p hr polyenute/L/(Byron #2oO manufactured by Toyobo)...
1 phr Example 3 When the liquid composition in Example 1 was changed to the following,
A long film sample having about 1,000,000/□1.12 particulate protrusions with a height of 100 people and having microgel particles as cores was obtained. This sample is designated as C.

Liquid composition: Microgel particles made of divinylbenzene (average diameter: 160) 0.1 phr Sodium dodecyl sulfate ・・・・・・・・・・・・・・・
Trace amount of water ・・・・・・・・・
・・・・・・ 2 phr Methyl ethyl ketone ・・・・・・・・・・・・1000 phr
Holyester (Byron Boo)・・・・・・・・・0.
5 phr Example 4 Made of polyethylene terephthalate containing almost no particulates due to residual polymerization catalyst, the surface was roughened by coating and curing a liquid mainly consisting of a modified silicone emulsion containing a thickener during film formation and stretching. A sample obtained by applying the same coating treatment as in Examples 1 to 3 on a polyethylene terephthalate biaxially stretched film on which a thin layer of different polymers consisting of fine wavy irregularities was formed was used. Let them be L and M, respectively. The particulate resin protrusions formed on the surfaces of these samples correspond to A to C, respectively.
It was in almost the same condition as the one.

Comparative Example 1 The branutic films themselves used in Examples 1 to 3 and Example 4 are referred to as samples S and T, respectively.

Example 6 Eleven samples of A to Q, M, S, and T were connected to each other, and a CoNi ferromagnetic metal thin film (Ni = 20 wt% film thickness: 100 μm) was formed on the surface by continuous vacuum oblique evaporation method. was formed in the presence of trace amounts of oxygen. The oxygen content of the magnetic layer was 6% in terms of atomic ratio to metal.

After that, various types of 7-bone solution were applied to the surface of each sample, and magnetic tape was made by slitting it to a predetermined width.
In an environment of 90% R and H at °C, I hung it on a prototype video recorder and the rotating head was 1'! 1K TV state, envelope, and still life were determined by 4111. As a comparative example, for sample T, the vapor-deposited mI was heat-treated to precipitate polyester oligomer crystals on the surface, and then the same vapor deposition as described above was performed to form e/Ih protrusions (about 300 in height) consisting of oligomer crystals 75). A magnetic tape was formed after applying a lubricant solution to a sample with a density of approximately 100,000 particles/-, and a magnetic tape was formed without applying a lubricant solution to a specific sample among the above. The above measurements were also carried out on the sample.

These results are shown in Table 1.

Effects of the Invention As is clear from the above examples, the magnetic recording medium of the present invention does not generate squealing even in high humidity, has a good envelope, and exhibits stable running performance. Furthermore, it has a good Nutyl lifespan in high humidity, and has very high practical value.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of embodiments of the magnetic recording medium of the present invention, respectively. 1.11...Substrate, 2,2'-...Particle core, 3'...Binding resin, 4.4'...
Ferromagnetic metal thin film, 6゜61...Lubricant.

Claims (1)

[Claims] 1000/62 particulate resin protrusions with a particle height of 30 to 500 people with core microgel particles made of crosslinked polymers
1. A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on a plastic film substrate provided with an undercoat layer having the above structure, and a lubricant is present on the thin ferromagnetic metal film.