JPS6120223A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording material having excellent durability, excellent impact resistance, water resistant and solvent resistance and high quality by providing a magnetic layer on a non-magnetic base and a protective layer consisting essentially of an org. high polymer contg. a fluorine graft polymer thereon. CONSTITUTION:The non-magnetic base includes resin films consisting of polyethylene terephthalate, PP, cellulose acetate, cellulose diacetate and polyimide, paper, synthetic paper and aluminum foil. The magnetic particles which are one component to constitute the magnetic layer includes gamma-Fe2O3, Fe3O4, Co-contg. gamma-Fe2O3, Co-contg. Fe2O4, Co-deposited gamma-Fe2O3, etc. The protective layer to be provided on the magnetic layer is constituted by using the org. high-polymer material contg. the fluorine graft polymer as the essential component. The fluorine graft polymer is obtd. by copolymerizing a general-purpose monomer and fluorine monomer by a radial polymn. method and is used at 0.1-5%, more preferably 0.2-2% with respect to the org. high polymer material.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to magnetic recording media used as magnetic tapes, floppy disks, magnetic cards, and the like.

Prior Art Most of the magnetic recording media used as magnetic tapes, floppy disks, magnetic cards, etc. are those in which a magnetic layer containing magnetic particles and a binder is provided on a non-magnetic support such as paper or plastic film. be.

These types of magnetic recording media often slide or come into contact with the magnetic head and guide members during recording, and as a result, even though they are not used many times, the magnetic layer wears out and the reproduction output decreases. This was the main cause of malfunctions.

In order to eliminate these inconveniences, for example (a) abrasives such as SiC, AltOs s Cr*Os, etc. are added to the magnetic layer to accelerate the wear of the magnetic head.
Alternatively, (b) attempts have been made to add lubricants such as silicone and wax;

The actual situation is that the method (b) tends to cause phenomena such as softening of the magnetic layer film and cylindrical clouding, so that the amount of the additive used is inevitably limited and cannot bring about sufficient effects.

Other means include (c) a retaining layer made of a lubricant, (c) a protective layer containing abrasive particles dispersed in a resin binder, or (e) lamination or mixing of various resin binders on the magnetic layer. Providing a protective layer has also been conventionally used, but good results have not yet been obtained with these methods.

That is, in (c) above, the life of the protection layer is short;
In the case of (E), the wear resistance is good, but the impact resistance is poor, or vice versa.Furthermore, it has poor durability and water resistance, especially when used for magnetic cards. Solvent resistance is still insufficient.

@I The purpose of the present invention is to eliminate the above-mentioned defects, to have excellent wear resistance and therefore durability, and to have almost no drop in playback output even after many recordings and playbacks (in addition, it has good impact resistance, water resistance,
The present invention provides a high-quality magnetic recording material with excellent solvent resistance.

Structure The magnetic recording medium of the present invention is characterized by providing a magnetic layer on a non-magnetic support and a protective layer containing an organic polymer containing a fluorine-based graft polymer thereon.

As a result of various studies to achieve the above object, the present inventor found that by providing a protective layer made of an organic polymer containing a specific additive on the magnetic layer, the electromagnetic conversion characteristics of the magnetic layer are not impaired. Furthermore, it has been found that a high-quality magnetic recording medium can be obtained that has excellent wear resistance, durability, and impact resistance, as well as excellent water resistance and solvent resistance. The present invention was completed based on such knowledge.

The present invention will be explained in more detail below. Other members of the present invention except for the protective layer, ie, the non-magnetic support and the magnetic layer itself may be completely the same as conventional ones.

Therefore, as a non-magnetic support used in the magnetic recording medium of the present invention, ? Examples include resin films such as riethelene terephthalate, borif pyrene, cellulose triacetate, cellulose diacetate, and polyimide, paper, synthetic paper, and aluminum foil.

The magnetic particles, one of the components constituting the magnetic layer, are as follows:
r-Fe, 0. , Fa, 04. Co-containing r
-FezOg.

Co-containing Fe104, Go adhesion r-FezOg
are cited as representative examples.

The binder used as the other component constituting the magnetic layer together with the magnetic particles includes those commonly used in this field.
For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-styrene/copolymer,
Urethane elastomers, polyvinyl butyral, cellulose acetate butyrate, nitrocellulose, polyester resins, styrene/butadiene/copolymers, butadiene/acrylonitrile copolymers, and the like are used. Further, an electron beam curable binder may be used. The method for manufacturing magnetic recording media using this rice binder for forming the magnetic layer is advantageous in terms of prevention of solid content in the magnetic layer forming liquid, improvement of pot life, simplification of the manufacturing process, energy saving, etc. . Furthermore, a combination of an electron beam curable binder and a thermosetting binder can also be effectively used.

Typical examples of electron beam curable binders include compounds having an ester skeleton, ether skeleton, urethane skeleton, epoxy skeleton, etc., specifically oligomers or prepolymers having an acryloyl group, methacryloyl group, etc., such as urethane acrylate. Examples include oligomers, polyester/acrylate polymers, polyether/acrylate prepolymers, epoxy/acrylate grebolymers, polyester/urethane/acrylate prepolymers, and the like. On the other hand, examples of the thermosetting binder include urethane resins, epoxy resins, cellulose resins, and mixtures thereof with vinyl chloride 114B'ft, vinylidene chloride resins, and the like. In addition, dispersants, antistatic agents, lubricants, abrasives, hardening agents, etc. commonly used in this field may be appropriately added to the magnetic layer.

The protective layer provided on the magnetic layer as described above is composed of an organic polymer material containing a fluorine-based graft polymer. The fluorine-based graft polymer referred to herein is a comb-shaped gelasto polymer obtained by copolymerizing a general-purpose monomer and a fluorine-based monomer by a radical polymerization method. Examples of the versatile monomer include maleic ester, α-olefin/vinyl ether, vinylsilane, allyl ester, vinyl ester, acrylonitrile, styrene, acrylic ester, methacrylic ester, and diene. In addition, fluorine-based seven drugs
Examples include tetrafluoroethylene, chlorotrifluoroethylene vinylidene fluoride, and vinyl fluoride. The fluorine-based graft polymer obtained by graft copolymerizing these materials has a 0.0.
1% to 5% (preferably 0.2-2%) is used.

Note that various thermosetting resins and thermoplastic resins can be used as the organic polymer material. For example, examples of the thermosetting resin include epoxy resin, phenol resin, melamine resin, and urea resin. Thermoplastic resins include cellulose resin, acetal resin, acrylic resin, vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, polyester resin, etc. Examples include listyrene resin, polyurethane resin, polycarbonate resin, polyamide resin, and copolymers thereof.

In order to actually produce the magnetic recording material of the present invention, first, a magnetic layer forming liquid and a protective layer forming liquid are prepared, and these are sequentially applied onto a support and dried (in the case of forming a protective layer, drying is followed by heat curing). Bye. Examples of solvents used to prepare these forming liquids include acetone, methyl ethyl chloride, cyclohe'tf7, vinegar (19F), toluene, xylene, hexane, and heptane. Gravure coating, reverse roll coating, barcode coating, knife coating, etc. can be appropriately employed.

The protective layer thus formed exhibits appropriate slipperiness and good water and oil resistance, and exhibits excellent abrasion resistance, impact resistance, water resistance, and oil resistance as a protective film for the magnetic layer. This is a fluorine-based graft polymer that is uniformly mixed in a protective layer forming liquid containing an organic polymer material. It is presumed that this is because of this.

In any case, the thickness of the magnetic layer is suitably about 1 to 20 microns, while the thickness of the protective layer is suitably about 0.5 to 5 microns.

Next, Examples and Comparative Examples will be described. Note that all parts are parts by weight.

Example 1 75 parts of l-Fe203 powder, 3 parts of lecithin, 15 parts of vinyl chloride-vinyl acetate-vinyl alcohol copolymer, 7 parts of polyurethane distomer, and 190 parts of toluene/methyl ethyl lactone mixed solvent (volume ratio 1:1) After dispersing the mixture in a l-lumil for 24 hours, 3 parts of a polyisocyanate compound was added thereto and kneaded to prepare a magnetic layer forming liquid.

The above magnetic layer forming liquid was applied onto a polyester film having a thickness of 180 μm and dried to form a magnetic layer having a thickness of about 13 μm. Furthermore, a protective layer forming liquid having the following composition was applied onto the magnetic layer, dried, and then heat treated to form a protective layer with a thickness of about 3 μm.
The obtained magnetic recording medium was cut to a specified size to form a magnetic card.

Polyester resin (Byron 200 manufactured by IL Yobo Co., Ltd.)
10 parts fluorine-based graft polymer (Aron GF-300 manufactured by Toagosei Co., Ltd.)
0.5 parts toluene/methyl ethyl ketone mixed solvent (volume ratio 1:1) 42@Example 2 Acrylic resin (Aron S-2060 manufactured by Toagosei Co., Ltd.) as a protective layer forming liquid
10 parts Fluorine graft polymer (Aron GF-300 manufactured by Toagosei Co., Ltd.) 0.
5 parts toluene/methyl ethyl ketone mixed solvent (volume ratio 1
:1) A magnetic card was produced in exactly the same manner as in Example 1 except that a composition consisting of 4zs was used.

Comparative Example 1 A magnetic card was produced by providing a polyethylene wax protective layer (approximately 3 μm thick) in place of the protective layer of Example 1.

Comparative Example 2 A magnetic card was produced by providing a protective layer made of a mixed system of acrylic resin and nitrocellulose resin (weight ratio 1:1) in place of the protective layer of Example 1.

When these four types of magnetic cards were tested for abrasion resistance, impact resistance, water resistance, and solvent resistance, the results shown in Table 1 were obtained.

(The following is a blank space) Effects As is clear from the above description, the magnetic recording medium of the present invention is particularly excellent in abrasion resistance, durability, impact resistance, as well as water resistance and solvent resistance.

This is considered to be due to the fact that the surface protective layer is composed of a resin layer containing a fluorine-based graft polymer arranged in a comb shape as described above.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer is provided on a non-magnetic support and a protective layer made of an organic polymer material is provided thereon, a fluorine-based graft polymer is contained in the organic polymer material of the protective layer. A magnetic recording medium characterized by: