JPS61123017A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To diminish surface roughness without spoiling durability by using a polyurethane resin and vinyl chloride resin contg. the metallic salt of a sulfonic acid as a binder. CONSTITUTION:The resins contg. the metallic salt of the sulfonic acid are used for both resins used for a magnetic recording medium contg. the polyure thane resin and vinyl chloride resin as a binder and the vinyl chloride resin in which an epoxy group is incorporated at 0.1-3wt% is used. The magnetic powder to be used is exemplified by iron oxide, Co-contg. orion oxide or metal lic iron, Fe-Co, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-Co-B, Fe-Co-Cr-B, etc. Nitrocellulose, nitrocellulose derive., polyester resin, buyral resin, phenoxy resin, etc. are also added if necessary as the binder.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium that can be used for audiotague, videotague magnetic disks, and the like.

Conventional configurations and their problems In recent years, efforts have been made to smooth the magnetic layer, particularly in video tapes, in order to improve electromagnetic conversion characteristics. Attempts have been made to make the magnetic powder finer, more highly dispersed, and use a smoother base film, but there are still areas to be improved regarding the binder. Polymers alone are rarely used as binders for magnetic recording media because durability is important. Various polymer combinations have been proposed in order to improve durability while maintaining moderate dispersibility, but none of them can be said to be satisfactory.

OBJECTS OF THE INVENTION The object of the present invention is to provide a magnetic recording medium with improved electromagnetic characteristics by reducing surface roughness without impairing durability.

Structure of the Invention The present invention provides a magnetic recording medium using a polyurethane resin and a vinyl chloride resin as a binder, in which both resins contain a sulfonic acid metal salt, and the vinyl chloride resin has an epoxy group of 0.1 to 3% by weight. This is a magnetic recording medium characterized by tW.

Description of examples Fine particles of magnetic powder to smooth the magnetic layer.

While achieving high dispersion and using a smooth base film, we have achieved excellent runnability without impairing electromagnetic conversion characteristics.
In order to improve the durability of the magnetic recording medium, it is usual to use a combination of two or more types of binders, rather than a single polymer. Therefore, not only the dispersibility of the polymer in magnetic powder, carbon black, abrasive, etc. becomes a problem, but also the compatibility of the polymers used with each other plays a large role in smoothing the magnetic layer. Among these, polyurethane resins containing sulfonic acid metal salts are known to have good dispersibility with respect to magnetic powder. The present inventors conducted extensive research on polymers that have good compatibility with polyurethane resins containing metal sulfonates and have sufficient coating film strength. As a result, they found that the polymers have excellent dispersibility and coating stability, and have excellent coating film properties. The present invention has been achieved by finding a magnetic recording medium that is sufficient.

Iron oxide is used as the magnetic powder used in the present invention.

CO-containing iron oxide or metallic iron, Fe-co.

Fe-Ni, Go-Ni, Fe-Go-N
i, Fa-Go-B.

Examples include Fe-Go-0r-B. In addition to the compounds of the present invention, nitrocellulose can be used as a binder.

Nitrocellulose derivatives, polyester resins, phthyral resins, phenoxy resins, etc. can also be added as necessary.

Lecithin or oleic acid is used as a dispersant.

Higher fatty acids such as valmitic acid can be used. As the abrasive, α-alumina, α-Fe205° chromium oxide, etc. are used. As an antistatic agent, conductive carbon such as Kettin Black E and C1 can also be added.

Various kneaders are used to mix and disperse magnetic paint. For example, three-roll mills, agitator mills, ball mills, pebble mills, sand grinders, high-speed impeller dispersion machines, high-speed stone mills, high-speed impact mills, dispersers, attritors, kneader-1 high-speed mixer homogenizers, ultrasonic dispersion machines, etc. Used in combination.

5-7 chloride containing sulfonic acid metal salt and epoxy group Vinyl resin can be easily obtained as follows.

The vinyl chloride monomer and glycidyl acrylate can be copolymerized and then cleaved with sulfonic acid, followed by the desired metal salt. Expressed as a reaction formula, it becomes as follows.

Below margin 6 To vane 7-1 The content of epoxy groups in the above-mentioned vinyl chloride copolymer is 0.1 to 3% by weight, and more preferably ldo, 5%.
~2 weight class. If the content is less than 0.1% by weight, the viscosity tends to increase after the paint is manufactured.

If the content exceeds 3 parts by weight, the vinyl chloride copolymer becomes brittle and the physical properties of the coating film deteriorate.

The present invention will be further explained in detail below.

Example 1 Ferromagnetic Go coated iron oxide oleic acid 1 part by weight Polyurethane resin containing sulfonate and lithium groups
Vinyl chloride-vinyl alcohol copolymer containing 10 parts by weight of potassium sulfonate groups (2 parts by weight of epoxy foundation)
10 parts by weight α-alumina (average particle size 0.3μ
m) 5 parts by weight Carbon black, S-170 (trade name of Deguza Corporation) 4 parts by weight Palmitic acid 1 part by weight Pentyl stearate 1 part by weight MEK-Toluene-MIBK (2:2:1) 200 parts by weight The above composition The mixture was mixed and dispersed for 5 hours using an attritor and a sand grinder to obtain a magnetic paint.

Next, 4 parts of Coronate L (polyisocyanate (trade name: 9 Nippon Polyurethane Co., Ltd.)) is added, and the mixture is filtered through a filter with an average pore size of 1 μm. It is coated on a 14 μm thick polyethylene terephthalate film, oriented, dried, polished to a mirror finish, and then cured. Furthermore, a back coat layer containing a carbon blank and calcium carbonate as main components was provided on the polyethylene terephthalate on the opposite side to the magnetic layer to obtain a magnetic tape.

Comparative Example 1 Vinyl chloride containing no epoxy group in Example 1
A magnetic tape was obtained in the same manner except that a vinyl alcohol copolymer was used.

9 page 7 Example 2 Iron oxide f in Example 1 Fe -Go -Ni alloy comparative example 2 Niraporan N-2304 which does not contain sodium sulfonate groups instead of the polyurethane resin containing sodium sulfonate groups in Example 2 A magnetic tape was obtained in the same manner except that (trade name of polyurethane resin manufactured by Nippon Polyurethane Co., Ltd.) was used.

Example 3 Ferromagnetic metal iron powder 10, (long axis 0.20 μm, short axis 0.025 μm J10
0 parts by weight silicone oil 1 part by weight lecithin
Polyurethane resin containing 1 part by weight sulfo/acid potassium group
12 parts by weight Vinyl chloride containing sodium sulfonate groups tx-Fe2035 parts by weight Kennan Plack IjC0 2 parts by weight myristic acid 1 part by weight butyl stearate 1 part by weight MEK-)Luene-cyclohexano/ (weight ratio 2:2:1) ) 200 parts by weight of the above composition was mixed and dispersed for 6 hours using a pressure kneader and an agitator mill to obtain a magnetic coating material.

After adding 4 parts of Desmosil L (trade name of polyisocyanate manufactured by Bayer AG) and stirring with a disper, the average pore diameter was 1 μm.
Filter with a filter.

11P-7゜Coating on 10 μm thick polyethylene terephthalate, orientation, drying, mirror polishing, and then curing. Furthermore, a Banokko-1 layer containing carbon black as a main component was provided on the polyethylene terephthalate on the opposite side to the magnetic layer to obtain a magnetic tape.

Comparative Example 3 Vinyl chloride containing no epoxy group in Example 3
A magnetic tape was obtained in the same manner except that a vinyl alcohol copolymer was used.

Each of the obtained magnetic tapes was cut into inch pieces, wound into a cassette half, and the C/N at sMITz was measured. The video tape for G/N measurement was a VHS video tape recorder (MV-9800 manufactured by Matsushita Electric Industrial Co., Ltd.), and in the case of iron or alloy magnetic material, the recording/reproducing head was changed to Sendust alloy.

As the standard tape, National Video Tape, Super HG120 (NY-TI 20HG) manufactured by Matsushita Electric Industrial Co., Ltd. was used, and its C/N was set to 6oaB. Durability is 200 when the tape is placed in an environment of 40°C and so%RH.
The condition was observed after passing. The surface roughness was measured using Taliserf manufactured by Rank Taylor Hobson and expressed in Ra. Ra means the arithmetic mean of the deviations of the surface roughness from the center line.

The results are shown below.

Effects of the Invention As is clear from the Examples and the corresponding Comparative Examples, the present invention has improved dispersibility in terms of surface roughness, and therefore the Examples have an improved C/N of 13 b-7.

Regarding durability, in the comparative example, powder falling off and clogging were noticeable after about 70 to 100 passes.

From the above, it is clear that the present invention is effective in terms of surface roughness, C/N, and durability.

Claims (2)

[Claims] (1) A magnetic recording medium in which a magnetic layer is formed by applying a magnetic paint in which metal or alloy ferromagnetic powder is dispersed in a binder onto a non-magnetic support, which contains a sulfonic acid metal salt as the binder. A magnetic recording medium characterized by using polyurethane resin and vinyl chloride resin. (2) The magnetic recording medium according to claim 1, wherein the vinyl chloride resin contains 0.1 to 3% by weight of epoxy groups.