JPH0697501B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having excellent running durability and winding characteristics.

[Prior Art] Conventionally, as a magnetic recording medium such as a video tape, an audio tape, a memory tape, and a magnetic disk, a magnetic layer in which ferromagnetic fine powder is dispersed in a binder is provided on one surface of a non-magnetic support. The one having a back layer on the other surface is widely used.

Various measures are taken to improve the running durability of such a magnetic recording medium, for example, 100 mμ ~ 50 in the back layer.
The running durability has been improved by adding coarse particles (for example, carbon black) of about 0 mμ to slightly roughen the surface properties, or by adding a lubricant in the back layer.

[Problems to be solved by the invention]

However, although the running durability is improved by the above method, slippage between the magnetic layer and the back layer is improved, which causes winding disorder. Therefore, there is a demand for measures to improve winding characteristics as well as running durability.

Therefore, an object of the present invention is to provide a magnetic recording medium which is excellent in running durability and winding characteristics.

[Means for solving problems]

The present inventors have added a non-magnetic powder having an average particle size of 1 μm to 3 μm to a back layer having a thickness of about 2.5 μm or less to form protrusions having a height of about 1.0 μm to 2 μm on the surface of the back layer of 30 to 30 μm. 200
The present invention has been accomplished by finding that the above object can be achieved by forming the particles / mm ² .

That is, the present invention provides a magnetic recording medium in which a magnetic layer in which ferromagnetic fine powder is dispersed is provided on one surface of a non-magnetic support and a back layer is provided on the other surface, and the thickness of the back layer is 1.0 μm.
m-2.5 μm, and BaSO ₄ , CaCO in the back layer.
₃ , non-magnetic powder (coarse particle filler) having an average particle size of 1 μm to 3 μm selected from ₃ , SiO ₂ , benzoguanamine resin, and bentonite, and a height of 1.0 μm to the back layer surface.
The magnetic recording medium is characterized by including protrusions of 2 μm so that 30 to 200 protrusions / mm ^{2 are} formed.

Hereinafter, the present invention will be described in detail.

The ferromagnetic fine powder used in the present invention includes γ-Fe
₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , FeOx (1.33 <x ≦ 1.5), Co
-FeOx (1.33 <x ≤ 1.5) -containing ferromagnetic iron oxide, chromium dioxide, ferromagnetic alloy powder, etc., which have been conventionally used for coating type magnetic recording media, can be used.

As the binder used in the magnetic layer and the back layer of the present invention, conventionally used thermoplastic resins, thermosetting resins,
A reactive resin or a mixture of these is used.

The thermoplastic resin has a softening temperature of 150 ° C. or lower, an average molecular weight of 10,000 to 300,000, and a degree of polymerization of about 50 to 2000, such as vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, vinyl chloride vinyl acetate. Vinyl alcohol copolymer, vinyl chloride vinyl acetate maleic anhydride copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester vinylidene chloride copolymer, acrylic acid Ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon-
Silicone resin, nitrocellulose-polyamide resin,
Polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene Copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber thermoplastic resins, and mixtures thereof are used.

As a thermoplastic resin or reactive resin,
The molecular weight is 200,000 or less, and by heating after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Further, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, phenoxy 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 resin. And isocyanate prepolymer mixture, methacrylate copolymer and diisocyanate prepolymer mixture, polyester polyol and polyisocyanate mixture, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate mixture, polyamine Resins and mixtures thereof.

In the present invention, additives usually used in the magnetic layer, such as lubricants, antistatic agents, and abrasives, may be added as necessary.

The feature of the present invention lies in the back layer. The back layer has a dry thickness of 1.0 μm to 2.5 μm, preferably 1.0 μm to 2 μm. When the thickness of the back layer is 1.0 μm or less, it is difficult to retain the non-magnetic powder having a particle size in this range in the back layer, and when it is less than 1 μm, it becomes difficult to apply. Average particle size 1 μm to 3 μm, preferably 1.5 μm to 2.5
It contains non-magnetic powder (coarse particle filler) of μm. If the average particle size is smaller than 1 μm, the desired protrusion cannot be formed, and if it is larger than 3 μm, the particles cannot be retained in the back layer, and powder drop occurs to increase dropout.

Such non-magnetic powder in the back layer, high protrusions 10μm~2μm the back layer surface is added so as to be 30 to 200 pieces / mm ² formed.

In order to form such protrusions, 0.1 to 20% by weight, preferably 1.0 to 15% by weight, of the co-magnetic fine powder (and relaxation with other powders if they exist), Preferably 5.0 to 15% by weight is added.

If the addition amount is less than 0.1% by weight, the desired projection is not formed, and if it is more than 20% by weight, the effect of the back layer on the magnetic layer cannot be ignored and the electromagnetic conversion characteristics deteriorate.

When an appropriate protrusion is formed on the back layer surface in this way,
In the running system, the frictional force at each part is reduced, running durability is increased, and when the tape is wound, the protrusions on the back layer surface are hard to get into the magnetic layer side, improving winding characteristics and preventing winding misalignment. It is presumed that it is preventing.

As the coarse particle filler used in the present invention, BaSO ₄ , C
A non-magnetic powder selected from aCO ₃ , SiO ₂ , benzoguanamine resin, and bentonite is used.

If necessary, carbon black and other additives can be added to the back layer.

As the organic solvent used when dispersing, kneading and coating each of the above components to form the magnetic layer and the back layer in the present invention, ascent, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone at any ratio,
Ketones such as tetrahydrofuran; alcohols such as methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol; methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol monoethyl acetate. Ester type such as ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether,
Ether type such as dioxane; Tar type (aromatic hydrocarbon) such as benzene, toluene, xylene, cresol, chlorobenzene, styrene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Chlorinated hydrocarbons, N, N-dimethylformaldehyde, hexane, etc. can be used.

The material of the support used in the present invention, polyethylene terephthalate, polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose triacetate, cellulose derivatives such as cellulose diacetate, vinyl resins such as polyvinyl chloride, polycarbonate, polyamide, Examples include plastics such as polysulfone.

The magnetic recording medium of the present invention can be obtained by coating each of the above components on the support and drying the support to provide a magnetic layer and a back layer. The back layer may be provided before or after the magnetic recording layer. In the case of a magnetic recording layer,
After the application, it is dried while being locally oriented, and subjected to surface treatment such as calendering if necessary.

〔Example〕

 Next, examples and comparative examples of the present invention will be shown.

In each example, "part" means "part by weight".

A magnetic paint prepared by the composition and method described below was applied to the surface of a polyethylene terephthalate base (nonmagnetic support) having a thickness of 20 μm so that the thickness after drying was 6.0 μm, and dried.

Next, a back layer coating solution prepared by the composition and method described below was applied to the polyethylene terephthalate surface on which the magnetic coating material was not applied so that the thickness after drying was 2.0 μm.

After coating, a drying process and a surface smoothing treatment were performed, and the film was immediately wound.

The wound web was then heat-cured at 40 ° C. for 48 hours, and then the web was slit into a 1-inch width to obtain a 1-inch video tape.

Magnetic coating composition Co-containing γ-Fe ₂ O ₃ 100 parts (Specific surface area: 35 m ² / g powder Hc: 650 Oe) Vinyl chloride / vinyl acetate / maleic anhydride copolymer 15 parts (MPR-TM, Nisshin Chemical Co., Ltd. Nitrocellulose 5 parts Polyurethane resin 6 parts (Crisbon 6119, Dainippon Ink and Chemicals, Inc.) Carbon black 3 parts (Average particle size: 20 mμ) Cr ₂ O ₃ 3 parts Oleic acid 2 parts Stearic acid Butyl 1 part Stearic acid 0.5 part Fatty acid modified silicone 2 parts Oleic acid amide 0.5 part Butyl acetate 240 parts Methyl ethyl ketone 120 parts The above composition was put into a ball mill and kneaded and dispersed for 48 hours, and then a polyisocyanate compound (Coronate L-75, Japan 10 parts of Polyurethane Co., Ltd. was added, and the mixture was further kneaded and dispersed for 1 hour. After kneading and dispersion, a magnetic paint was obtained by filtering using a filter having an average pore size of 1 μm.

Back layer coating liquid composition The above composition was put in a ball mill and kneaded and dispersed for 70 hours, then 19.1 parts of a polyisocyanate compound (Coronate L-75, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added, and the mixture was further kneaded and dispersed for 1 hour. After kneading and dispersion, the mixture was filtered using a filter having an average pore size of 3 μm to obtain a back layer coating solution.

Table 1 shows the results obtained by performing the following evaluation tests on the obtained samples.

Running durability Tape 1 was run 50 times at a speed of 10 m / sec with the device shown in FIG. 1, the back layer was observed, and the rank was divided into four ranks according to the degree of scratches. The distance between the two rolls of the device is 50 cm, SU
The diameter of the S pole 2 was 0.5 cm.

A: It doesn't hurt at all.

B: 2-3 scratches.

C: There are 4 or more scratches, and shavings adhere slightly to the pole.

D: There are 4 or more scratches, and shavings adhere to the pole.

Winding characteristics Amprex VTR "VPR-3" is used to evaluate the condition of the winding end face when rewound at 50 times speed.

A: The end faces are neatly arranged.

B: The end surface is rough, but there is no protrusion.

C: One or two places pop out.

D: Three or more jumps out.

C / S / N ratio Measured according to the BTS standard. The values shown are the values when the output level of the standard tape (1 inch video tape prepared in Comparative Example 1) is 0 dB.

Number of protrusions Using a three-dimensional rough surface measuring unit (Surfcom 300B system) manufactured by Tokyo Seimitsu Co., Ltd., height x length x width = 2000 x 10
Draw a three-dimensional surface roughness chart at a magnification of 0 × 200, and read the number of protrusions of 1 μm to 2 μm from the chart.

[Effects of the Invention] As is clear from the results shown in Table 1, when the back layer according to the present invention is provided, the magnetic recording is excellent in both running durability and winding characteristics and magnetic characteristics (CS / N). The medium is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for testing the running durability of a magnetic recording medium. 1 ... tape, 2 ... SUS pole

Front page continuation (72) Inventor Kazuo Hasumi 2-12-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd. (56) Reference JP-A-52-102004 (JP, A)

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer having ferromagnetic fine powder dispersed on one side of the non-magnetic layer and a back layer on the other side of the magnetic layer. 2.5
μm, and BaSO ₄ , CaCO ₃ , Si in the back layer.
Nonmagnetic powder having an average particle size of 1 μm to 3 μm selected from O ₂ , benzoguanamine resin and bentonite, and 30 to 200 protrusions with a height of 1 μm to 2 μm on the back layer surface.
^2. A magnetic recording medium characterized by including as formed.