JPS6252714A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form a magnetic recording medium having excellent running stability and durability by forming a lubricative coating layer consisting of the cured matter of a specific fluoropolymer. CONSTITUTION:The lubricative coating layer consisting of the cured matter of the fluoropolymer having a fluoroalkyl group and hydrolyzable functional group or silyl group having halogen atoms is provided on the front of a thin ferromagnetic film or the rear surface of a substrate after said thin film is provided as a magnetic layer on the substrate. The effect of a low friction characteristic and excellent corrosion resistance is developed by the fluoroalkyl group and the polymer is crosslinked and cured by the hydrolyzable functional group or silyl group having halogen atoms, by which the toughness, wear resistance and the adhesiveness to the magnetic layer, etc. are improved. A protective layer may be provided of this polymer alone or in conjunction with other surface treating agents.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides lubrication on a ferromagnetic metal thin film provided on a substrate by vacuum evaporation, ion silating, snobbing, plating, etc. and/or on the back surface of the substrate. The present invention relates to a surface-modified magnetic recording medium formed by forming a coating layer.

The purpose is to improve the running stability, durability, and corrosion resistance of magnetic recording media that use ferromagnetic metal thin films as recording media.

[Prior art and its problems]

In recent years, instead of magnetic recording media made by coating and drying ferromagnetic metal powder together with a binder on a substrate, a magnetic layer of a thin ferromagnetic metal film, which has excellent high-density magnetic recording properties, has been deposited on the substrate. Magnetic recording media deposited by sputtering etc. are used for audio recording, video recording and 8%
It has attracted particular attention as a recording memory for video recording tapes, perpendicular magnetic recording, magneto-optical disks, and the like.

However, this metal magnetic layer is easily corroded by oxygen, moisture, etc. in the air, and is also easily worn out by running in contact with magnetic heads, drums, posts, etc. Therefore, it is necessary to improve the corrosion resistance and abrasion resistance of the surface of the tape without degrading the electromagnetic conversion characteristics, and to provide the tape with low friction, a thin and uniform thickness, and strong adhesion and flatness. Much research and development has been carried out on lubricating surface treatment agents and treatment methods that enable this.

One method that has been proposed so far is to use adsorption with the surface of a metal thin film to absorb lubricants (higher fatty acids and their salts, fatty acid amides, fluorinated surfactants, etc.), wax, silicone oil, fluorinated A method of applying a treatment agent such as oil-based oil has also been proposed, but this method reduces friction against the magnetic head etc. and temporarily improves durability, but it also prevents the treatment agent from volatilizing with use.
It is difficult to maintain the effect for a long time once the stain has been removed.

In addition, by alloying the magnetic material itself to make it highly hard, or by forming a film of other metals or inorganic compounds such as silicon compounds by methods such as vapor deposition or sintering, a coating with high hardness and corrosion resistance can be obtained. This method is effective in improving corrosion resistance and abrasion resistance, but the adhesion is insufficient, and because of the high hardness of the blade, the recording medium and transporter rapidly In addition to problems such as destruction of the metal, it requires complicated processing and is expensive, and satisfactory results have not been obtained.

Alternatively, the surface of the magnetic layer or the back surface of the substrate may be coated with urethane resin, silicone resin, fluororesin, epoxy resin, etc.
Many proposals have been made to coat with polymeric substances such as ester resins and radiation- and ultraviolet-curable resins. This has a temporary effect on low friction, corrosion resistance, durability, etc., but considering that it causes a decrease in electromagnetic conversion characteristics called spacing loss, the polymer material coating has a
It must have a film thickness of about 00X, preferably about 200X, and a uniform and smooth planarity. However, with such a film thickness, it is difficult to completely prevent moisture from entering, and there are problems in terms of frictional fluctuations during running, and in terms of wear resistance and chemical resistance. Furthermore, it is difficult to form a uniform thin film with little output fluctuation by surface treatment by coating a known polymeric substance.

Also, for the back side of the base, it is strongly required to provide wear resistance and lubricity to improve tape squeal, running stability, and durability. It has also been proposed to form a polymer layer containing a lubricant and then apply a non-stick coating layer.

However, in any case, according to the prior art, a product that is satisfactory as a protective layer for a ferromagnetic metal thin film or as a backside treatment agent for a substrate has not yet been obtained.

[Means for solving problems]

The present inventors have arrived at the present invention as a result of intensive research to overcome the drawbacks of the known methods proposed in the past.

The object of the present invention is to eliminate the various drawbacks of the prior art described above, and to provide a magnetic layer on the surface of a magnetic layer of a ferromagnetic metal thin film provided on a substrate by vacuum evaporation, ion blasting, sputtering, plating, etc. and/or on the back surface of the substrate. It is an object of the present invention to provide a magnetic recording medium provided with a uniform protective film having low friction, excellent wear resistance, and corrosion resistance without deteriorating electromagnetic conversion characteristics.

An example of the magnetic recording medium according to the present invention is a polyethylene terephthalate film (hereinafter referred to as PET film).
Fa+Co+Nl is deposited on a substrate such as a polyimide film or a polyamide film, or a polycarbonate plate, an acrylic resin plate, or a glass plate by vacuum evaporation, ion derating, sputtering, or plating.
tcr, Ga.

After providing a ferromagnetic metal thin film of a magnetic metal such as Go or an alloy mainly composed of these as a magnetic layer, (a) a fluoroalkyl group and (b) a fluoroalkyl group and (b) ) A lubricating coating layer consisting of a cured product of a fluorine-based polymer having a hydrolyzable functional group or a halogen atom and a silyl group, which exhibits excellent effects of low friction and corrosion resistance due to the fluoroalkyl group, and is hydrolyzable. The polymer is crosslinked and cured by the silyl group having a functional group or a halogen atom, making it strong, having excellent wear resistance, and improving adhesion to magnetic layers, etc. IJ Mama - A protective film is provided by itself or in combination with other surface treatment agents.

In the present invention, after providing the magnetic layer, in order to improve the durability and adhesion of the magnetic layer, a polymer compound or an inorganic compound (S
A base layer may be formed by performing base treatment such as formation of tO2@ and alloying of the magnetic material itself, and then a lubricating coating layer may be formed.

The alkyl group carbon number of the fluoroalkyl group in the polymer used in the present invention is 1 to 20. Preferably, the pressure is in the range of 4 to 20. When the number of carbon atoms in the alkyl group exceeds 20, the above-mentioned improvement in performance is likely to be lost.

Hydrolyzable functional groups in the polymer used in the present invention include alkoxy groups, acetoxy groups, and (QC2H4) described below.
, OR4. Further, as the halodane atom, chlorine is most preferable.

Polymer used in the present invention (hereinafter abbreviated as the present invention polymer)
The manufacturing method uses a radically polymerizable monomer having a fluoroalkyl group (hereinafter referred to as fluoromonomer), a radically polymerizable monomer having a silyl group (hereinafter referred to as silyl monomer), and in some cases, other monomers (hereinafter referred to as fluoromonomer). 3
Most preferred is radical copolymerization using the king of the seven polymers.

As the above-mentioned fluoromonomer, the following can be mentioned.

OR CF3(CF2), (CH2)1. OCC=CM
2R CF, (CF2), (CH2)40CC=CI(2F3 OR CF3CH20CC= CH2 OR cmr2rn+, (cH2)2occ=ca2(m=4
to 14) and fluorine-based macromonomers.

Here, R is a hydrogen atom or a methyl group, and X is F or CF.
, , i represents an integer from 2 to 7. Among these fluoromonomers, the fluoroalkyl group has 4 to 2 alkyl groups.
0 is preferred.

There are ~20 examples. Furthermore, regarding fluorine-based macromonomers, for example, the above-mentioned fluoromonomers are radically polymerized in the coexistence of thioglycolic acid to obtain a molecular weight of 1.0.
00-10.00 (1) Obtain a one-end carboxylic acid prepolymer and react with glycidyl methacrylate to obtain a fluorine-based macromonomer having a methacrylic acid ester end group.

Examples of the silyl monomer include acrylate silanes and/or methacrylate silanes (hereinafter collectively referred to as (meth)acrylate silanes).

Other silanes that can be radically copolymerized include:

Ethylene-based silanes shown in the following can be mentioned.

R1 is a hydrogen atom or a methyl group, R2 and R are a methyl group, an ethyl group, or a phenyl group, and n is an integer of 1 to 3. m is O or 1, and t is 0 to 1 when m = O
An integer of 2, 2 for mzl. X is an alkoxy group,
acetoxy group, general formula %) group (R4 is a hydrogen atom, methyl group, ethyl group, n
is an integer from 1 to 5).

Specifically, r-C meth)acryloyloxyprobyl dimethoxysilane, r-(meth)acryloyloxypropylmethyldimethoxine, r-(meth)acryloyloxypropyl dimethoxysilane, 3-(2- (meth)acryloyloxyethoxy)propyltrimethoxysilane, 3-(2-(meth)acryloyloxyethoxy)propylmethyldimethoxysilane, 3-(2-(
meth)acryloyloxyethoxy)probyldimethylmethoxysilane, 5-((meth)acryloyloxy)
Pentyltrimethoxysilane, 5-((meth)acryloyloxy)hentylmethyldimethoxysilane, 5-(
(meth)acryloyloxy)pentyl dimethylmethoxysilane, p-vinylphenyltrimethoxysilane,
p-vinylphenylmethyldimethoxysilane, p-vinylphenyldimethylmethoxysilane, r-(meth)acryloyloxynoropyltri(β-methoxyethoxy)
Examples include silane. Among these, r-methacryloxypropyltrimethoxysilane is most preferred.

Examples of the third monomer include olefinic compounds such as low molecular weight unsaturated hydrocarbons such as ethylene and propylene, vinyl halogenides such as vinyl chloride and vinyl fluoride, vinyl esters of organic acids such as vinyl acetate, styrene, and styrene. Substituted compounds and vinyl aromatic compounds such as vinylpyridine and vinylnaphthalene, acrylic acid and/or methacrylic acid (hereinafter abbreviated as (meth)acrylic acid),
N-vinyl compounds such as esters of (meth)acrylic acid, acrone, acrylonitrile, N-vinylpyrrolidone and N-vinylcaprolactam, and also maleic anhydride.

Examples include esters of maleic acid and fumaric acid, and radically polymerizable macromonomers other than fluorine-based ones.

As the third monomer, (meth)acrylic acid ester is most preferred. These monomers can be used alone or in combination of two or more.

As the radical copolymerization method, conventionally known methods can be used,
For example, radiation irradiation, a method using a radical polymerization initiator, etc. can be used, but a method using a zocal polymerization initiator is preferable in terms of ease of polymerization operation and ease of controlling the molecular weight. Any solution polymerization method, bulk polymerization method, or the like can be used, but contamination of water must be avoided.

The amount of fluoromonomer used was 100% of the above seven-mer mixture.
It is preferably 5 to 80 parts by weight, and more preferably 10 to 70 parts by weight. If it is less than 5 parts by weight, it is difficult to achieve the desired effects such as low friction and corrosion resistance, and if it exceeds 80 parts by weight, the desired effects tend to be less improved.

The amount of the silyl monomer added is preferably 0.01 to 50 parts by weight per 100 parts by weight of the monomer mixture, and more preferably 0.5 to 37 parts by weight. If the silyl monomer is less than 0.01 part by weight, the curability of the polymer of the present invention tends to be poor, the adhesion with the magnetic layer decreases, and it is difficult to obtain excellent wear resistance.

If the amount exceeds 50 parts by weight, improvements in excellent effects such as adhesion and abrasion resistance tend to decrease.

If the polymer of the present invention obtained as described above is used alone, it will not only improve adhesion, low friction, abrasion resistance, corrosion resistance, etc. on the surface of the magnetic layer, but also provide a similar excellent coating layer on the back surface of the substrate. can be formed and fully achieve the intended purpose.

The proportion of the third monomer is preferably 950 to 70 parts by weight, more preferably 10 to 70 parts by weight, per 100 parts by weight of the monomer mixture, in view of the compatibility of the polymer of the present invention with the solvent-soluble surface treatment agent. desirable.

Furthermore, it can be used in combination with other surface treatment agents mentioned below. Even if the polymer of the present invention is added and dissolved in this surface treatment agent and this fluorine-based graft polymer dissolved surface treatment agent is coated on the surface of the magnetic layer or the back side of the substrate, the desired purpose can be achieved with excellent results. In some cases, it is better than the case alone. This is because the polymer of the present invention has extremely excellent surface migration ability, so if it is added to a surface treatment agent and formed into a film in a normal environment, that is, in the air or in an inert gas such as nitrogen, the polymer of the present invention/IJ polymer will be transferred to the surface of the coating film. - This migrated polymer, which can be migrated and concentrated and can easily modify the coating surface, is its compatible component (component based on the third monomer)
Due to its anchor effect, it does not easily fall off from the coating surface, and the modification effect lasts for a long time.

Therefore, a coating layer that can fully achieve the object of the present invention can be obtained.

In the present invention, when a surface treatment agent in which the polymer of the present invention is dissolved is used as a top coat or a back coat,
The surface treating agent that can be used is preferably a surface treating agent that dissolves the polymer of the present invention and is compatible with components compatible with the polymer of the present invention.

The surface treatment agent is composed of a polymer or a polymer and a solvent. / IJ moms include, for example, α, β-ethylenically unsaturated monomers, α, β-ethylenically unsaturated carboxylic acids, and polypolymers of these derivatives, polymers produced by polycondensation reactions, polymers, etc. In addition to being able to use the polymer itself, such as a polymer produced by an addition reaction, a curable composition comprising a radically polymerizable component can also be used as a polymer precursor. Here are some specific examples of polymers.

Examples of α, β-ethylenically unsaturated monomers include styrene, acrylonitrile, and vinyl chloride, and examples of α, β-ethylenically unsaturated carboxyl acids include monovalent and dihydric acids such as (meth)acrylic acid and maleic acid. Value Cal? Examples include phosphoric acid.

Also α,β-ethylenically unsaturated Cal? Examples of derivatives of phosphoric acid include alkyl esters of (meth)acrylic acid, such as esters such as ethyl, butyl, and 2-ethylhexyl, and examples of hydroxyalkyl esters of acrylic acid or methacrylic acid include hydroxyethyl (meth)acrylate. , hydroxypropyl ester, etc. Examples of surface treatment agents include air-drying lacquers and baking-type clear enamels obtained by polymerizing a combination of these monomers.

Examples of the polymer obtained by the polycondensation reaction include linear polyester resins, alkyd resins, polyamide resins, epoxy resins, etc. obtained by ordinary polycondensation reactions. Also, as for polymers produced by polyaddition reactions, can they be obtained by ordinary polyaddition reactions? Examples include urethane resin and polyurea resin. Other examples include silicone resins and fluororesin coating agents.

It was. Cellulose IL conductors such as ethyl cellulose, butyl cellulose, and nitrocellulose can also be used in combination with these four reamers. When using a curable composition consisting of a radically polymerizable component as a polymer precursor,
A method of thermal polymerization curing using a radical polymerization initiator, a method of redox polymerization curing using a combination of a radical polymerization initiator and a polymerization curing accelerator at around room temperature, ultraviolet curing using a photopolymerization initiator, or photopolymerization initiation. There are various types of curing means, such as electron beam curing, which may or may not use agents, and any composition that can be polymerized and cured by such means can be used.

Examples of radically polymerizable components include (meth)acrylic acid ester monomers, unsaturated/lyesters, polyester (meth)acrylates, urethane (meth)acrylates, epoxy (meth)acrylates, and polyamides (
Examples include meth)acrylates and thiol/ene polymers.

The amount of the polymer of the present invention added to the surface treatment side is preferably 1.00% by weight or more based on the 4-limer or radically polymerizable component of the surface treatment agent. If the amount added is less than 1.00% by weight, the intended effect cannot be sufficiently exerted on the surface of the coating film.

Although these surface treating agents can be used either dissolved in an organic solvent or not dissolved in an organic solvent, it is generally preferable to use them as organic solvent type surface treating agents. It increases the solubility of the fluorine-based graft polymer, increases the migration of the fluorine-based graft polymer to the coating surface, and improves the orientation of the fluorine component to the surface, making it possible to form a thin film that does not adversely affect electromagnetic conversion characteristics. This is because a uniform smooth surface can be obtained due to the reduction in viscosity. Usable solvents include hydrocarbon solvents such as toluene, xylene, and cyclohexane; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; and methyl selon rub, ethyl cellosolve, etc. Among these various solvents, one or a mixed solvent of two or more is preferably used. Depending on the means used to apply the treatment agent, additives such as antistatic agents, extender pigments, waxes, and railing agents may be added.

As a method for curing the above-mentioned fluoropolymer alone or optionally a surface treatment agent, it is also possible to crosslink and cure the fluorine-based polymer as it is by catalyzing moisture present in the air or on the surface of the substrate at room temperature or by heating. In Although,
A method of crosslinking and curing using a crosslinking and curing catalyst such as dibutyltin dilaurate and dibutyltin maleate is preferred because of its good crosslinking efficiency.

In addition, it has a curing agent depending on the type of surface treatment agent used, such as the above-mentioned hydroxyl group. j? +7
When using polymer as a surface treating agent, the surface treating agent can be cured using an incyanate compound, and when using the radically polymerizable composition as the surface treating agent,
The surface treatment agent is also cured by heat, ultraviolet light, or electron beams.

The above-mentioned fluorine-based graft polymer alone or in combination with the above-mentioned various processing agents has a lubricating property and is applied onto substrates such as various plastics and glass by vacuum deposition, ion blasting, sputtering, plating, etc. The coating is applied to the surface and/or back side of the substrate of various types of recording media such as tapes, perpendicular recording and magneto-optical disks made of thin ferromagnetic metal films, but this method varies depending on the shape of the recording medium. Coating, gravure offset, slit reverse coating, spray coating, spinner coating, dipping coating, curtain flow coating, etc. are applied to the surface and dried, and the surface of the magnetic layer and/or the back surface of the substrate is coated with several or more smooth layers. It is possible to form a coating layer that meets the desired purpose using a film that is suitable for the desired purpose, and it is possible to achieve excellent effects that have not been achieved before.

[Embodiments of the invention]

Next, the present invention will be explained with reference to synthesis examples, working examples, and comparative examples, but these are only some of the many experiments and should not be limited to these. Incidentally, "part" on each side represents part by weight, "chi" represents weight %, and the coefficient of friction during running of the vapor-deposited tape was determined by the following formula.

Synthesis Example 1 CnF2n, CH2CH20CCH=CH2 (!1=8
．． ．． 10.12.14 mixture) 50 parts, 50 parts of γ-methacryloxypropyltrimethoxysilane as a silane monomer, methyl ethyl ketone (MEK) as a solvent
200 parts and 2 parts of azobisinbutyronitrile (hereinafter abbreviated as AIBN) as a radical polymerization initiator were placed in a flask equipped with a condenser, a stirrer, and a thermometer, and reacted for 4 hours at a temperature of 90°C in a nitrogen atmosphere. The present invention?
I got lmari.

Synthesis Example 2 Fluoromonomer: CnF2n+, CH2C)I20CCI(=CH2(n
=8. IO, 12, 14) 50 parts, 25 parts of r-methacryloxypropyltrimethoxysilane as the silane monomer, 25 parts of stearyl methacrylate (hereinafter abbreviated as SMA) as the third monomer, M as the solvent.
200 parts of EK, AlBN2 as a radical polymerization initiator
The reaction was carried out in the same manner as in ① using 1 part. After the reaction is complete,
When MEK was removed by vacuum distillation, a slightly yellow, highly viscous oily reaction product was obtained.

Synthesis Example 3 Use of fluorine-based macromonomer A glass flask equipped with a stirrer, a reflux condenser, two dropping funnels, a thermometer, and a gas inlet was charged with 200 parts of pensitrifluoride, and one dropping funnel (referred to as dropping funnel A) was charged with 200 parts of pensitrifluoride. ) K 200 parts of fluoroacrylate having the following structure, 7.08 parts of 3-mercaptopropionic acid, 4 parts of azobisisobutyronitrile, and 1 part of pencitrifluoride in the other dropping funnel (referred to as dropping funnel B).
00 parts of the mixed solution was added. After introducing nitrogen gas, the temperature of the flask was increased, and the reaction solution was added dropwise through dropping funnel A and dropping funnel B over 2 hours while keeping the reaction solution at 70°C. After further reaction for 4 hours, the polymerization conversion rate of fluoroacrylate was 95.
, 8%. Next, the reaction solution was heated, refluxed for 2 hours, and then cooled to maintain the solution temperature at 90°C.

To this were added 0.1 part of hydroquinone monomethyl ether, 13.95 parts of glycitul methacrylate, and 51 parts of tetrabutylammonium bromide z. Furthermore, the nitrogen gas was switched to air blowing, and the reaction was carried out at 90° C. for 6 hours. The reaction conversion rate determined from titration with base was 94.6.
It was Chi.

The reaction solution was poured into 10 times the volume of methanol to cause precipitation. 5
Solid fluorine-based macro 7mer 15 dried under reduced pressure at 0℃
2.3 parts were obtained.

ZengCF, -(-CF2-)nCH2CH20CCH=CH
2n = 4 to 12 mixture (average value of n approximately 7) 50 parts of the fluorine-based macromonomer thus obtained, 25 parts of r-methacryloxypropyltrimethoxysilane as the silane monomer, and SMA 25 as the third monomer.
1 part, 200 parts of pencitrifluoride as a solvent, and 200 parts of AIBNZ as a radical polymerization initiator were placed in a flask equipped with a condenser stirrer and a thermometer, and 8 parts of pencitrifluoride was added as a solvent in a N2 atmosphere.
The reaction was carried out at a temperature of 0° C. for 8 hours to obtain a polymer of the present invention.

Example 1 80%Co-20% was deposited by vacuum evaporation method while forcibly introducing oxygen gas onto a 12 μm thick PET film.
A evaporated tape was obtained by forming a magnetic layer of a ferromagnetic alloy thin film made of N1.

Next, the present invention 4? obtained in Synthesis Example 3? Dibutyltin dilaurate (catalyst) was added to the remer alone at a concentration of 0.5% relative to the polymer, and this was mixed into methyl ethyl ketone/ethyl acetate/toluene =: 3/1.510.5
(1114M of surface treatment agent was dissolved in a mixed solvent with a weight ratio of It was cured by drying with hot air for a minute to form a lA smooth coating layer with a thickness of about 300X.

Further, after preparing a backside treatment agent with a concentration of 15ts by dissolving a composition having the following component ratio in a mixed solvent of methyl ethyl ketone/ethyl acetate/toluene = 2/l/1 (mixing ratio), this treatment agent was applied to the tape. It was coated on the back side using a gravure coating method and dried with hot air at 90° C. for 3 minutes to form a lubricating coating layer with a thickness of about 1 μm.

〔Composition〕

0 Polymer of the present invention obtained in Synthesis Example 3 30 parts 0 Copolymer of acrylic polyol (weight average molecular weight approximately 5oo
oo methyl methacrylate/butyl acrylate/styrene/2-hydroxyethyl methacrylate copolymer) 43 parts 0/!
J7') Rofluoroethylene mother powder (manufactured by Hoechst Japan: TF-9205) Is the 3-part o-derivation a sex car? Columbia Carn 5 parts Q xylene diisocyanate (curing agent) 18.9g
0.1 part of O diptyltine dilaurate (curing agent) Example 2 A composition with the following component ratio was dissolved in a mixed solvent of methyl acetate) 7/ethyl acetate/toluene = 3/1.510.5 (weight ratio). A surface treatment agent with a concentration of 1 was prepared. Subsequently, this treatment agent was applied onto the magnetic layer of the same vapor-deposited tape as in Example 1 using the slit reverse coating method, and then cured by hot air drying at 90°C for 3 minutes. A coating layer was formed.

〔Composition〕

0 20 parts of the polymer of the present invention obtained according to Synthesis Example 2
55 parts of polyol-type acrylic copolymer with an average molecular weight of 5oooo, 25 parts of 0 xylene diisocyanate (curing agent). Also, a lubricating coating layer with a thickness of 1 μm was formed on the back side of the tape using the same back treatment agent as in Example 1. did.

Example 3 To the polymer of the present invention obtained in Synthesis Example 1 alone, dibutyltin dilaurate (catalyst) was added in an amount of 0.
A surface treatment agent having a concentration of 3% was prepared by dissolving this in a mixed solvent of methyl ethyl ketone/ethyl acetate/toluene = 371.510.5 (weight ratio). Subsequently, using this treatment agent, a lubricating coating layer having a thickness of about 300× was formed on the magnetic layer of the vapor-deposited tape in the same manner as in Example 1.

Further, a lubricating coating layer having a thickness of 1 μm was formed on the back surface of the tape using the same back surface treatment agent as in Example 1.

Comparative Example 1 Stearic acid was dissolved in a mixed solvent of toluene/MEK=1/1 (weight ratio) to prepare a surface treatment agent with a concentration of 3%. Next, this treatment agent was applied onto the magnetic layer of the same vapor-deposited tape as in Example 1 by the slit-lino coating method, and cured by hot air drying at 90°C for 2 minutes. A lubricating coating layer of about 300X was formed.

In addition, the composition of the present invention/IJ mom in the composition constituting the back surface treatment agent of Example 1 was replaced with methyl ethyl ketone/
A back surface treatment agent having a concentration of 15% was prepared by dissolving it in a mixed solvent of ethyl acetate/toluene = 2/1/1 (weight ratio). Subsequently, this treatment agent was coated on the back side of the tape using a gravure coating method, and dried with hot air at 90° C. for 3 minutes to form a lubricating coating layer with a thickness of about 11 Rn.

Comparative Example 2 A compound having an acrylic double bond with the following structural formula and an alkoxy group in silicon in the molecule was dissolved in a mixed solvent of methyl ethyl ketone/isobutyl ketone = l/1 (weight ratio) to 3%. A concentration of surface treatment agent was prepared. Subsequently, this treatment agent was applied onto the magnetic layer of the same vapor-deposited tape as in Example 1 by the slit reverse coating method, and then
Dry with hot air at 90℃ for 1 minute, and then dry with electron beam for 15 minutes.
Irradiation was performed under M rad conditions to form a lubricating coating layer with a thickness of approximately 300 mm.

CH3 - (CH2CH)7.1 0H=CH2 Furthermore, a lubricating coating layer with a thickness of 1 μm was formed on the back surface of the tape using the same back surface treatment agent as in Comparative Example 1.

Comparative Example 3 A composition with the following component ratio was mixed with toluene/MEK=1/1 (
After preparing a surface treatment agent with a concentration of 3% by dissolving it in a mixed solvent with a weight ratio of ℃, hot air drying for 3 minutes to a thickness of approximately 300X
A lubricating coating layer was formed.

〔Composition〕

Polyol-type acrylic copolymer with an average molecular weight of 80,000 60 parts 0 xylene diisocyanate (curing agent)
38 parts 0 fatty acid ester (glycerin monostearate); lubricant 2
Furthermore, a lubricating coating layer with a thickness of 1 μm was formed on the back surface of the tape using the same back surface treatment agent as in Comparative Example 1.

Therefore, the characteristics of the vapor deposited tapes of Examples 1 to 3 and Comparative Examples 1 to 3 with lubricant coating layers formed on the front and back surfaces were investigated. The results are shown in the table below.

From the results in the above table, the magnetic recording medium obtained by the present invention does not deteriorate the electromagnetic conversion characteristics and is stable with low friction, whereas the medium according to the comparative example has a friction coefficient that increases when running or repeatedly running. It has good running properties and has excellent low wear and corrosion resistance. In addition, the back side of the base has excellent low friction and stability, and dew condensation occurs between the back side and the scratched surface of the reel, hub, etc.)
Good results were obtained without causing blocking.

Example 4 Has very good surface properties (surface roughness approximately 0,0 O5
A perpendicular magnetic recording medium was obtained by forming a Co--Cr magnetic layer with perpendicular anisotropy by sputtering on a PET film 411z substrate with a thickness of 5011 m (μm) and a thickness of 5011 m.

Next, a perfluoroalkyl ethylene oxide adduct (manufactured by Sumitomo 3M; Florard FC-430) was added to the polymer of the present invention obtained in Synthesis Example 3 to give a concentration of 3% to the polymer, and this was added to methyl isobutyl ketone. /ethanol/xylene = 2/l/1 (weight ratio) was dissolved in a mixed solvent to prepare a surface treatment agent with a concentration of 2.

Subsequently, this processing agent was applied onto the magnetic layer of the recording medium by spinner coating, and then dried with hot air at 90° C. for 5 minutes to form a lubricating coating layer with a thickness of about 100 to 150×.

The obtained perpendicular magnetic recording medium of Example 4 had excellent friction properties and wear resistance, and was also excellent in corrosion resistance and environmental resistance. In addition, good results were obtained in the contact start-stop test, and no abnormalities such as surface scratches were observed.

〔Effect of the invention〕

As described in detail above, according to the present invention, a top coat layer can be formed on the surface of the magnetic layer with excellent wear resistance, wear resistance, lubricity, corrosion resistance of the magnetic layer, and adhesion with the magnetic layer, and a top coat layer with excellent adhesiveness with the magnetic layer can be formed on the back surface of the substrate. It is possible to form a paracote (1) with excellent abrasion resistance, lubricity, and adhesion to the substrate.

The protective film formed in this way does not adversely affect the magnetic layer, does not often deteriorate the electromagnetic conversion characteristics, and has low friction and excellent corrosion and abrasion resistance, resulting in improved running stability and durability. It is possible to provide an excellent magnetic recording medium.

Claims (1)

[Claims] 1. (a) a fluoroalkyl group and (b) a silyl group having a hydrolyzable functional group or having a halogen atom on the surface of the magnetic layer made of a ferromagnetic metal thin film provided on the substrate and/or on the back surface of the substrate A magnetic recording medium comprising a lubricating coating layer made of a cured fluoropolymer.