JPH01282729A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having high durability, high wear resistance and high load resistance by forming a top coat layer consisting of an org. phosphate compd. and amine compd. on a magnetic layer. CONSTITUTION:The magnetic layer essentially consisting of the ferromagnetic powder and binder is provided on a nonmagnetic base and the top coat layer consisting of the org. phosphate compd. and the amine compd. is formed on said magnetic layer. The org. phosphate is exemplified by, for example, (R1O)3P, (R1O)3P=0, etc.; where R1 denotes a hydrocarbon group of 6-22C, and may be a satd., unsatd., straight chain or branch group. The amine compd. is the compd. expressed by formula I and the hydrocarbon group thereof may be a satd., unsatd., straight chain or branched group. In formula I, R1 denotes a hydrogen atom or hydrocarbon group of 1-8C; R2 denotes a hydrogen or hydrocarbon group of 1-8C; R3 denotes a hydrocarbon group of 1-18C. The magnetic recording medium having such high durability, high wear resistance and high load resistance to withstand severe requirements for durability is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium with excellent durability.

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support, in which a top coat layer made of an organic phosphate ester compound and an amine compound is formed on the magnetic layer, or a top coat layer is formed on the magnetic layer. By forming a top coat layer made of an amine compound on the magnetic layer and internally adding an organic phosphate ester compound to the magnetic layer, a magnetic recording medium having high durability, high abrasion resistance, and high load carrying capacity is provided. That is.

[Conventional technology]

In general, magnetic recording media are formed by coating a magnetic layer containing dispersed magnetic powder on a non-magnetic support, such as magnetic tape, magnetic sheet, magnetic card, magnetic disk, etc.
There are many types of magnetic drums, and each type is widely used depending on its purpose.

Among the above-mentioned magnetic recording media, for example, magnetic disks have undergone remarkable development in recent years, with a transition from large-diameter 8-inch disks to small-diameter 2-inch disks. In the case of the above magnetic disk, the recording wavelength becomes shorter as the disk diameter becomes smaller, and in order to improve the contact characteristics, the contact method between the magnetic head and the magnetic disk has become more severe. Therefore, it is necessary for the magnetic disk to ensure sliding durability, contact start/stop (C3S) durability, and the like.

Conventionally, in order to ensure and improve the various durability of magnetic disks, studies have been conducted such as adding various abrasives, additives, and lubricants to the magnetic layer, and applying overcoating and puncture coating to the magnetic disk. is being carried out. For example, in JP-A No. 58-108033, a magnetic recording medium using a phosphoric acid ester of higher fatty acid and higher aliphatic alcohol as a lubricant is proposed, with the aim of ensuring and improving running stability and durability. .

[Problem that the invention seeks to solve]

However, in recent years, the contact system between a magnetic head and a magnetic disk has become very strict, and greater durability than ever has been required. Therefore, a magnetic recording medium using a lubricant made of a phosphoric acid ester of a higher fatty acid and a higher aliphatic alcohol as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 58-108033 cannot obtain a sufficient lubricating effect. This is because fatty acids that form a film on the metal surface initially exhibit good durability, but as the fatty acids gradually penetrate into the coating, they deteriorate the bonded part of the magnetic powder, resulting in durability. This is because it leads to sexual deterioration. Furthermore, the heat generated by sliding exceeds the melting point of the fatty acid coating, causing the fatty acid to fall off from the metal.

Therefore, it is possible to use an organic phosphate ester that has an accelerated reaction to the heat generated by sliding as a lubricant. However, it has been found that organic phosphate ester alone does not exhibit any lubricating effect because it has poor reactivity and the coating is destroyed before the organic phosphate film is formed on the metal surface.

Therefore, the present invention has been proposed in view of the above-mentioned conventional situation, and has high durability, high abrasion resistance, and high load-bearing capacity that can sufficiently withstand severe demands for durability. The purpose is to provide a magnetic recording medium.

[Means for solving problems]

As a result of intensive research aimed at achieving the above object, the present inventors have found that a lubricant composed of an organic phosphoric acid ester compound and an amine compound exhibits a very good lubricating effect.

That is, the magnetic recording medium of the present invention is a magnetic recording medium having a magnetic layer mainly composed of ferromagnetic powder and a binder on a non-magnetic support. The invention is characterized by forming a top coat layer made of a phosphoric acid ester compound and an amine compound, and the second invention is characterized by forming a top coat layer made of a phosphoric acid ester compound and an amine compound. The magnetic recording medium is characterized in that a top coat layer made of an amine compound is formed on the magnetic layer, and an organic phosphate ester compound is internally added to the magnetic layer.

In the first invention, the mixing ratio of the organic phosphoric acid ester compound and the amine compound is 95:5 to 25 near 5 as parts by weight.
It is preferable that it is within the range of .

If it is less than 95;5, the effect of the amine compound cannot be expected much, and if it exceeds 25;5, the effect of the organic phosphoric acid ester compound will be small.

In the second invention, the proportion of the amine compound in the top coat layer is preferably 0.05 to 2.0% by weight, and the proportion of the organic phosphate compound internally added to the magnetic layer is based on 100 parts by weight of the magnetic powder. , preferably 0.1 to 2 parts by weight.

The organic phosphate esters are O (R, O) 2P-011, (RIO) P -(Ol
l) z, (R+0)P-(OH) tll and the like. However, R1 represents a hydrocarbon group having 6 to 22 carbon atoms, which may be saturated, unsaturated, linear, or branched, and in which part or all of the hydrocarbon group is substituted with a perfluoro group. It may be something.

The amine compound has the general formula: R, -N-R2, (wherein R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and R2 represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. group, and R3 represents a hydrocarbon group having 1 to 18 carbon atoms), and the hydrocarbon group may be saturated, unsaturated, linear, or branched, and the hydrocarbon group may be saturated, unsaturated, linear, or branched. It may be one in which part or all of the hydrogen groups are substituted with perfluoro groups.

The magnetic powder used in the present invention is not particularly limited as long as it is used in coating type magnetic recording media, and examples include γ-Fe, 03, FexOs,
Iron oxide with an oxidation state intermediate between r-FezO= and Fezes, Co-containing r-Ft403 and Fe, 0. Iron oxide in an oxidation state intermediate between the above, iron oxide containing one or more metal elements (especially transition metal elements), and iron oxide with a coating layer mainly composed of Co oxide or hydroxide. CrO2, the surface of CrQ□ is reduced to Cr
, O, oxide-based magnetic powder such as those with layers formed, Fes
Metals such as C0% N1, or Fe-Co alloy, Fe-
Ni alloy, Fe-Co-Ni alloy, Fe-Co-N1-
P alloy, Co-N1-Pe-B alloy, Fe-Ni-Zn
Fine ferromagnetic powders of iron-containing solid solutions such as alloys and Fe-Mn-Zn alloys can be used. In particular, the present invention exhibits very high effects when metal is used as the magnetic powder.

The magnetic paint used in the production of the magnetic recording medium of the present invention may be prepared by using a thermoplastic resin, thermosetting resin, reactive resin, or electron beam curing resin as a binder, or by adding a polarity to a predetermined one of these resins. It is possible to use so-called highly dispersible binders which have introduced groups to improve their dispersibility.

The thermoplastic resin used preferably has a softening degree of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 2,000, such as hinyl chloride-hinyl acetate 11, vinyl chloride - vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide, Examples include synthetic rubber-based thermoplastic resins such as polyvinyl butyral, cellulose derivatives (eg, nitrocellulose), polyester, and polybutadiene.

The thermosetting resin (reactive resin) is preferably one that has a molecular weight of 2,000,000 or less in the state of a coating liquid, and whose molecular weight increases due to reactions such as polymerization and addition when heated after coating and drying. Among these resins, those that do not soften or dissolve before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, nitrocellulose melamine resin, high molecular weight polyester. Mixtures of isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/
There are mixtures of triphenylmethane triisocyanates, polyamines and mixtures thereof.

By using polyisocyanate as a third component in combination with these resins, a three-dimensional network structure can be created and a magnetic recording medium with heat resistance and wear resistance can be produced. The ratio of polyisocyanate that can be blended is
It can be mixed up to about 5 to 5% (by weight) based on the total amount of the resin. If the proportion is small, the magnetic recording medium will generally become flexible. Also, if it is added in a large amount, it will become hard, but the use of the magnetic recording medium It may be selected as appropriate.

As the polyisocyanate, isocyanates having at least two isocyanate groups and adducts thereof are preferred, such as aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, alicyclic diisocyanates,
Examples include aromatic isocyanates, naphthalene isocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, and adducts thereof.

Organic solvents for magnetic paint include ketones such as acetone, methyl ethyl ketone, isobutyl ketone, and cyclohexanone, esters such as methyl acetate and ethyl acetate, ethers, polyhydric ethers such as polyoxymethylene and polyoxyethylene, benzene, and toluene. aromatic hydrocarbons, such as
It is selected from chlorinated hydrocarbons such as dichloromethane, chloroform, and carbon tetrachloride, taking into consideration polarity, boiling point, etc.

In producing the magnetic recording medium of the present invention, an abrasive and a lubricant may be further added to adjust the magnetic paint.

As the abrasive, aluminum oxide, silicon carbide, chromium oxide, etc. are added, and as the lubricant, silicon-containing polymer compounds such as dialkyl polysiloxane (alkyl group has 1 to 5 carbon atoms), dialkoxy poly Silicone oil such as siloxane (alkoxy group has 1 to 4 carbon atoms), alkyl alkoxysiloxane (alkyl group has 1 to 5 carbon atoms, alkoxy group has 1 to 4 carbon atoms), conductive fine powder such as graphite, Inorganic fine powders such as molybdenum disulfide and tungsten disulfide, olefin polymers such as polyethylene, polypropylene, polyethylene vinyl chloride copolymers, polytetrafluoroethylene, linear olefins that are liquid at room temperature, carboxylic acid esters, and the like are used. It is preferable to add the abrasive in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

Materials for the non-magnetic support used in the present invention include polyethylene terephthalate, polyethylene-2,6
- polyesters such as naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, In addition to plastics such as polycarbonate, polyimide, and polyamideimide, depending on the application, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these, ceramics such as glass, earthenware, and porcelain, paper, and baryta. Or polyethylene, polypropylene, ethylene-butene copolymer, etc. with 2 carbon atoms
Paper such as paper coated or laminated with α-polyolefins of 1 to 10 can be used. These non-magnetic supports may be transparent or opaque depending on the purpose of use.

Further, the form of the nonmagnetic support may be any film, tape, sheet, disk, card, drum, etc., and various materials are selected depending on the form.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Comparative Example 1 Metal magnetic powder 100 parts Vinyl chloride-vinyl acetate copolymer 10 parts Polyurethane
10 parts Cr, 03 10
Part carbon black 5 parts Methyl ethyl ketone 100 parts Toluene
100 parts sifro to xanon
100 parts of the above composition were mixed and dispersed in a sand mill system, then passed through a filter step, and then 5 parts of an isocyanate compound as a curing agent were added and stirred to obtain a magnetic paint. Apply 4 μm of this paint to a 33 μm thick base film.
It was applied to a thickness of m. After calendering, the magnetic disk was punched out into a disk shape with a diameter of 47mm.

Example 1 The composition of Comparative Example 1 with 1 part of phosphite added thereto was top coated with N,N-dimethyl-N-dodecylamine.

Example 2 Instead of N,N-dimethyl-N-dodecylamine in Example 1, N,N-dimethyl-N-oleylamine was top coated.

Example 3 The material of Comparative Example 1 was top coated with a mixture of phosphite and N,N-dimethyl-N-dodecylamine in a ratio of 2:1.

Comparative Example 2 A sample was prepared by adding phosphite to the composition of Comparative Example 1 and applying it.

The disks obtained above were assembled into jackets to be used as video floppy disks (VFDs), and continuous durability tests were conducted under various environments. Table 1 shows the evaluation results.

It was determined that the signal was not acceptable when the amount of signal attenuation was 3 dB.

By combining phosphite and amines in Examples 1 to 3 of Table 1, it is possible to guarantee durability over a wide range from low temperature to high temperature and low humidity to high humidity.

Comparative Example 1 shows good durability at room temperature, high temperature and high humidity, and low temperature, but only 1/10 of the durability at high temperature and low humidity.

Comparative Example 2 shows good durability under high temperature and low humidity, but poor durability under high temperature and high humidity.

Comparative Example 3 Metal magnetic powder 100 parts Vinyl chloride-vinyl acetate copolymer 10 parts Polyurethane
1st part Crz03 10
Part carbon black 5 parts Methyl ethyl ketone 100 parts Toluene
100 parts cyclohexanone
100 parts Lubricant 5 parts The above composition was mixed and dispersed in a sand mill system, then passed through a filter process, and then 5 parts of an isocyanate compound as a hardening agent was added and stirred to obtain a magnetic paint. This paint was applied to a 33 μm thick base film to a thickness of 4 μm. After calendering, the magnetic disk was punched out into a disk shape with a diameter of 47 m.

Comparative Example 4 One part of phosphite was added to the composition of Comparative Example 3, mixed, and applied.

Example 4 N,N-dimethyl-N was applied to the composition of Comparative Example 4.
- Top coated with dodecylamine.

Example 5 N,N-dimethyl-
Top coated with N-oleylamine.

Example 6 A phosphorous acid ester and N,N-dimethyl-N-dodecylamine (70;30) were added to the composition of Comparative Example 3 and mixed to form a top coat.

Example 7 Phosphite and N,N-dimethyl-N-dodecylamine (50:50) were added to the composition of Comparative Example 3 and mixed to form a top coat.

Example 8 The composition of Comparative Example 4 was top coated with phosphite and N,N-dimethyl-N-dodecylamine.

Comparative Example 5 A phosphate ester amine salt was added to the composition of Comparative Example 3 and applied.

The discs obtained in Examples 4 to 8 and Comparative Examples 3 to 5 were assembled into a jacket, and a video floppy disc (V
FD), continuous durability running tests were conducted under various environments, and the evaluation results are shown in Table 2.

When the signal attenuation amount was 3 dB, it was judged as unacceptable.

Compared to Comparative Example 3 in Table 2, adding phosphites (
It can be seen that in Comparative Example 4), the durability under high temperature and low humidity conditions is greatly increased, but on the other hand, the durability under high temperature and high humidity conditions is significantly deteriorated.

Comparative Example 5 was a case where a phosphate ester amine salt was used, and although there was some effect, it was insufficient.

〔Effect of the invention〕

As detailed above, the magnetic layer of the magnetic recording medium is top coated with an organic phosphate compound and an amine compound, or a top coat layer made of an amine compound is formed on the magnetic layer and the magnetic layer is coated with an organic phosphate ester compound. By internally adding a compound, the durability of the magnetic recording medium is greatly improved, and a magnetic recording medium having high durability, high wear resistance, and high load carrying capacity can be provided.

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer mainly composed of ferromagnetic powder and a binder on a non-magnetic support, an organic phosphate ester compound and an amine compound are provided on the magnetic layer. 1. A magnetic recording medium comprising a top coat layer formed thereon. 2. In a magnetic recording medium having a magnetic layer mainly composed of ferromagnetic powder and a binder on a non-magnetic support, a top coat layer made of an amine compound is formed on the magnetic layer, and the magnetic layer A magnetic recording medium characterized in that an organic phosphate ester compound is internally added to the magnetic recording medium.