JPS5922226A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a titled medium which maintains high merchandise value without deterioration in its durability and without the yellowing, etc. of its case upon long-term storage by dissolving the magnetic powder which is coated with a cobalt compd. on the surface and has >=7pH and nitrocellulose of a low degree of nitration as one of binders in a solvent, and thoroughly mixing the same to prepare a magnetic paint, coating the magnetic paint on a non-magnetic substrate and drying the same thereby forming the magnetic recording medium. CONSTITUTION:Compsns. consisting of 100 parts Co-deposited r-Fe2O3 (8.9pH), 15 parts nitrocellulose (10.7-11.5wt% degree of nitration), 15 parts a polyurethane resin, 5 parts carbon black, 1 part lecithin, 150 parts methyl ethyl ketone and 150 parts toluene are mixed for 20hr in a ball mill and after the mixture is filtered with a 3mu filter, the mixture is coated on a polyester film of 20mu thickness to 6mu thickness and is dried. The resulted magnetic tape is cut to a 1/2-inch width and the cut tape is incorporated in a cassette half. The cassette is put in white paper for packaging and is packaged with a transparent film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and relates to a so-called coated magnetic recording medium formed on a non-magnetic support and a layer consisting of magnetic powder and a binder.

It is already known that a magnetic recording medium using high coercive force magnetic powder in which only the surface of acicular ferromagnetic iron oxide is coated mainly with a cobalt compound has suitable magnetic properties, and such a magnetic recording medium is widely used as a high-density magnetic recording medium. This high coercive force magnetic powder is a dispersion of sword-shaped ferromagnetic iron oxide particles (Fe304 or r-Fe203).
Static turbidity o K, cobalt salt is added, cobalt ions are adsorbed on the surface of the sword-shaped ferromagnetic iron oxide particles, and excess; 11σ
After adding Qualunono 1no, is the dispersion 1 sound cloudy? (K to 10
(IC or more - +rσ) It is obtained by heating reaction with one history of θ groups.

In this way, a) ↑ high coercive force (l & force magnetic) 1 poor (j,) suitable (having magnetic properties 7 J''-1 pi- of the high coercive force magnetic powder) 1 is usually 8-1
It is 0. In addition, the r p of the magnetic powder is specified in the four-sided specification at °C.
HJ is the method described in JT, 81g5101 (
In other words, γ-Fe2031. Suspend 5 g of magnetic powder in 100 ml of pure water, boil for 5 minutes, and let the evaporated pure water cool to room temperature. Pl this supernatant liquid
This refers to the value measured using a meter (method of measuring with a meter).

Nitrocellulose is also widely used as a binder. Nitrocellulose has excellent dispersibility for magnetic powder, and is also used for A-loose in 21 and 21 rows.
The magnetic coating film has excellent surface properties and durability, and also has the advantage of low hygroscopicity.

By the way, the 4th edition of the magnetic journal has a magnetic coating made of a coercive force magnetic powder and a binder containing nitrocellulose applied on a non-magnetic support.
When stored for a long period of time, there are disadvantages in that durability deteriorates, the cassette half in which the magnetic recording medium is housed, and the white paper case for packaging turn yellow, resulting in a significant decrease in commercial value.

The present invention was made in view of these problems, and includes a magnetic powder with a pi-17 or higher, which has a core of ferromagnetic iron oxide and whose surface is coated with a cobalt compound, and a nitrification degree of 6.
The present invention relates to a magnetic recording medium in which a layer made of a binder containing 8 to 11.5 weight i% (in terms of N) of nitrocellulose is formed on a nonmagnetic support.

The nitrocellulose used in the present invention has a degree of nitrification of 6.
It is 8 to 11.5% by weight M% (in terms of N).

If the degree of nitrification is less than 6.8 weight, the dispersibility of the magnetic powder is poor and it cannot be used as a magnetic insect bite. Also, the degree of nitrification is 11.
If the number exceeds 5 and 11, the durability of the magnetic recording medium and the yellowing of the cartridge case and white packaging paper case cannot be improved.

In the present invention, a magnetic powder with a pH of 7 or more coated with a cobalt compound on the surface and nitrocellulose, which has a low degree of nitrification as one of the binders, is dissolved in a solvent and thoroughly mixed to form a magnetic coating 11, which is coated on a non-magnetic support. It is dried to create a magnetic recording medium.

As the binder, the nitrocellulose having a low degree of nitrification according to the present invention can be used in combination with other commonly used binders.

Commonly used binders include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, and acrylic acid. Ester-styrene copolymer, polyvinyl butyral, polyester resin, polyurethane resin, phenolic resin,
Examples include epoxy resin, polyamide resin, silicone resin, and the like.

Examples of solvents include ketones (e.g. acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone), alcohols (e.g. methanol, ethanol),
'Tetrahanol, butanol), esters (e.g. methyl acetate, ethyl acetate, butyl acetate,
Ethyl lactate, glycol acetate, monoethyl ether), glycol ether (example t) f ethylene
Clico-A/dimethyl ether, ethylene glycol monoethyl ether, dioxane), aromatic hydrocarbons (e.g. evabenzene, toluene, xylene), JIWflFj
&[Hydrogenides (e.g. hexane, heptane), nitropronochloride, etc. are used.

If necessary, lubricants, antistatic agents, abrasives, dispersants, etc. may be added to the magnetic paint.

Here, as the lubricant, higher fatty acid ester, silicone oil, fluorine oil, etc. are used.

As the antistatic agent, carbon particles, graphite particles, surfactants, etc. are used. As an abrasive, Cr2
O3, Al203, SiC, TiO2, r-Fe
Inorganic pigments such as zO3 are used. As the dispersant, higher fatty acids, metal soaps, higher alcohols, lecithin, etc. are used.

Examples of non-magnetic supports include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyethylene, and polyglot.

2 tons of polyolefins such as cellulose, cellulose diacetate, cellulose derivatives such as cellulose diacetate, vinyl resin, polyimide, polyamide, polycarbonate, etc. are used.

The present invention will be explained below with reference to examples.

Example C'o deposited r-Fe203 (pH 8,9)
' 100 parts nitrocellulose (nitrification degree 10.7-11
．． Five layers! 1%) l 5 tt polyurethane resin
151/carbon black
5″Resigun
l // methyl ethyl kene 1.
150” toluene 15
The ffi acids were mixed in a ball mill for 20 hours, filtered through a 3P filter, applied to a 20μ thick polyester film to a thickness of 6 1, and dried.

The obtained magnetic tape was then cut into 4 inch 11" pieces.
It was assembled into a cassette half, placed in a white paper packaging case, and wrapped with transparent film.

Comparative example Co deposited r-Fe203 (pI(8,9)
100 parts nitrocellulose (nitrification degree 11.6-12.
Double M%) 15〃Polyurethane resin
15〃Carbon Black 5〃
Lecithin 1 methyl ethyl ketone 150 toluene
15o//A magnetic tape was prepared using the above composition in the same manner as in the examples, assembled into a cassette half, placed in a white packaging paper case, and wrapped with a transparent film.

The magnetic tapes of Examples and Comparative Examples were 40 tl;, 80%R.
After being stored in a constant temperature and humidity chamber of I-I for 10 weeks, the durability (still time) of the magnetic tape and the degree of yellowing of the cassette half and the white paper case for packaging were observed.

From the above table, it can be seen that the magnetic recording medium of the present invention using the magnetic powder of < ptI 7 or higher and nitrocellulose with a low degree of nitrification has the same durability even when stored for a long period of time. It does not cause yellowing of cassette halves or white paper packaging cases.

Furthermore, if the pH of the high coercive force magnetic powder used in the present invention, in which only the surface of the acicular ferromagnetic iron oxide is coated with a cobalt compound, is brought closer to 7 by washing with water, etc., the effect will be even more effective.

As described above, the magnetic recording medium according to the present invention does not deteriorate its durability or cause yellowing of the case even during long-term storage.
High product value can be maintained.

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Claims (1)

[Claims] A magnetic powder with a pH of 7 or higher having a core of ferromagnetic iron oxide and a cobalt compound coated on the surface, and nitrified rci6. s
A magnetic recording medium characterized in that a layer made of a binder containing ~11.5 M% (in terms of N) of dicellulose is formed on a non-magnetic support.