JPS63249932A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve running durability and winding characteristic by adding nonmagnetic powder limited in average particle size into a back layer having about <=2.5mum thickness thereby forming projections of a specific height at a specific density to the surface of the back layer. CONSTITUTION:The thickness of the back layer is <=2.5mum and the nonmagnetic powder having 1-3mum average particle size is incorporated into the back layer in such a manner that the projections having 1-2mum height are formed at 30-200 pieces/mm<2> on the surface of the back layer. The nonmagnetic powder is added to fine ferromagnetic powder at 0.1-20wt.%, preferably 1.0-15wt.%, more preferably 5.0-15wt.% of the weight of said powder. The magnetic recording medium which excels in both the running durability and winding characteristic and has the excellent magnetic (C S/N) characteristics 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 running durability and winding characteristics.

[Conventional technology]

Conventionally, in magnetic recording media such as video tapes, audio tapes, memory tapes, and magnetic disks, a magnetic layer in which fine ferromagnetic powder is dispersed in a binder is provided on one side of a non-magnetic support, and a magnetic layer is placed on the other side of a non-magnetic support. Those provided with a back layer are widely used.

Various measures have been taken to improve the running durability of such magnetic recording media.
Coarse particles of ~500 mμ (e.g. carbon blank)
The running durability has been improved by adding a lubricant to make the surface rougher a little, or by adding a lubricant to the back layer.

[Problem that the invention seeks to solve]

However, although the above method improves the running durability, it also improves the slippage between the magnetic layer and the back layer, which causes curling. Therefore, measures are desired to improve running durability and winding characteristics.

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

[Means for solving problems]

The present inventors added non-magnetic powder with an average particle size of 1 μm to 3 μm to the hex layer having a thickness of about 2.5 μm or less, and protrusions with a height of about 0.5 μm to 2 μm on the surface of the hex layer. 5
It has been found that the above object can be achieved by forming ~100 pieces/1 san2, and the present invention has been achieved.

That is, the present invention provides a magnetic recording medium in which a magnetic layer in which fine ferromagnetic powder is dispersed is provided on one surface of a nonmagnetic support and a back layer is provided on the other surface, and the thickness of the back layer is 2.5 mm. 5
μm or less, and non-magnetic powder with an average particle size of 1 μm to 3 μm is placed in the back layer at a height of 0 on the surface of the back layer.
．． The magnetic recording medium is characterized in that it includes 5 to 100 protrusions of 5 μm to 2 μm/2 protrusions.

The present invention will be explained in detail below.

The ferromagnetic fine powder used in the present invention includes 7-Fe2
O3, Co-containing r -FezO,,,FeOx (1
, 33<X≦1.5), Co-containing FeOx (1,3
3< x≦1.5), etc., ferromagnetic iron oxide, chromium dioxide,
All materials conventionally used in coated magnetic recording media, such as ferromagnetic alloy powder, can be used.

As the binder used in the magnetic layer and back layer of the present invention, conventionally used thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof can be used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 300,000, and a degree of polymerization of about 50 to 2.
For example, vinyl chloride copolymer, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer. Polymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon-silicon resin, nitrocellulose-polyamide resin , polyfukkavinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (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-based thermoplastic resins, and mixtures thereof are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane curable resin, urea resin,
Melamine resins, alkyd resins, silicone resins, acrylic reactive resins, epoxy-polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, polyester polyols and polyisocyanate, urea formaldehyde resin, mixture of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.

In the present invention, additives commonly used in magnetic layers, such as lubricants, antistatic agents, abrasives, etc., may be added as necessary.

The feature of the present invention lies in the back layer. The back layer has a dry thickness of 2.5 μm or less, preferably 2 μm or less, and an average particle size of 1 μm to 3 μm, preferably 1.5 μm to 2.0 μm.
Contains 5 μm non-magnetic powder (coarse particle filler).

If the average particle size is smaller than 1 μm, the desired protrusions cannot be formed, and if the average particle size is larger than 3 μm, the particles cannot be retained in the backing layer, causing powder falling and increasing dropout.

Such non-magnetic powder is used in the back layer, and 5 to 100 protrusions with a height of 0.5 μm to 2 μm are formed on the surface of the back layer.
2. Add so that it forms.

In order to form such protrusions, 0.1 to 20% by weight, preferably 1.0 to 15% by weight of the ferromagnetic fine powder (and the sum of other powders if present) is used. It is added in an amount of 5.0 to 15% by weight, more preferably 5.0 to 15% by weight.

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

When appropriate protrusions are formed on the back layer surface in this way,
In the running system, the frictional force at each part is reduced, increasing running durability, and when the tape is wound, the protrusions on the back layer surface sink into the magnetic layer, improving the winding characteristics and preventing winding misalignment. It is presumed that this is being prevented.

The coarse particle filler used in the present invention includes BaSO
4. Powders such as CaCO3,5i02, henzoguanamine resin, and hentonite are used.

Note that carbon black and other additives can be added to the back layer as necessary.

In the present invention, the organic solvent used when dispersing, kneading, and coating the above-mentioned components to form the magnetic layer and back layer includes acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone,
Ketones such as tetrahydrofuran; alcohols such as methanol, ethanol, propatool, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol; methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol monoacetate Ester systems such as ethyl ether; Ether systems such as diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, and dioxane; Tar systems (aromatic hydrocarbons) such as benzene, toluene, xylene, cresol, chlorhenzene, and styrene; methylene chloride , chlorinated hydrocarbons such as ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene, and N,N-dimethylformaldehyde hexane.

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

The magnetic recording medium of the present invention can be obtained by applying each of the above components to the support and drying 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 coating, it is dried without being oriented in a magnetic field, and if necessary, surface treatment such as calendering is performed.

〔Example〕

Next, Examples and Comparative Examples of the present invention will be shown.

On each side, "parts" refer to "parts by weight."

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

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

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

The rolled original fabric was heat-cured in that state at a temperature of 40° C. for 48 hours, and then this original fabric was slit into 1-inch widths to obtain 1-inch video tapes.

1st raw JL material L or 5 Co content r = Fe203
100 parts (Specific surface area: 35r+?/g Powder Hc: 6500e) Vinyl chloride/vinyl acetate/maleic anhydride copolymer 15 parts (MP
R-TM, Nissin Chemical Co., Ltd.) Nitrocellulose 5 parts Polyurethane resin 6 parts (Crisbon 6119, Dainippon Ink Chemical Co., Ltd.) Carbon blank 3 parts (Average particle size: 20 mμ) Crz03 3
Part oleic acid 2 parts Butyl stearate 1 part Stearic acid 0.5 parts Fatty acid modified silicone 2 parts Oleic acid amide 0.5 parts Butyl acetate
240 parts Methyl ethyl ketone 120 parts The above composition was placed in a ball mill and mixed and dispersed for 48 hours, then 10 parts of a polyisocyanate compound (Coronate Shi-75, manufactured by Nippon Polyurethane) was added and mixed and dispersed for another hour. . After crosstalk dispersion, it was filtered using a filter having an average pore size of 1 μm to obtain a magnetic paint.

Back layer coating liquid composition Carbon blank (I) 50 parts (average particle size: 30 mμ) Carbon black (II) 5
0 parts (average particle size: 300 mμ) Oleic acid 0.5 parts Oleic acid amide 0.5 parts Cyclohexanone 40 parts Coarse particle filler Table 1 shows.

Methyl ethyl ketone 500 parts The above composition was placed in a ball mill and mixed for 70 hours at t4'
After drying, add a polyisocyanate compound (coronate).
75, made by Japan Polyurethane), add 19.1 parts,
Crosstalk was further dispersed for 1 hour. After crosstalk dispersion, 3μm
The solution was filtered using a filter having an average pore size of , to obtain a back layer coating solution.

The following evaluation tests were conducted on the obtained samples, and the results are shown in Table 1.

1 soybean after 50 minutes
The back layer was observed and divided into four ranks based on the degree of scratches. The distance between the two rolls of the same device is 5
The diameter of SOS ball 2 was 0.5 cm.

A: It won't hurt at all.

B: There are 2 to 3 injuries.

C: There are four or more scratches and a slight amount of shavings adheres to the ball.

D: There are four or more scratches and a considerable amount of shavings adheres to the pole.

R to 11th stop at 50x speed with mpex VTRrVPR-3J
The condition of the winding end surface during EW is evaluated as follows.

A: The end faces are neatly aligned.

B: The @ surface is rough, but there are no protrusions.

C: There are protrusions in one or two places.

D: There are protrusions in three or more places.

Measured in accordance with the Fuji S/N North BTS standard. Note that the values shown are values when the output level of the standard tape (1-inch videotape prepared in Comparative Example 1) is OdB.

Using a three-dimensional surface roughness measurement unit (Surfcom 300B system) manufactured by Tokyo Seimitsu ■, height x length x width = 200
A three-dimensional surface roughness chart is drawn at a magnification of 0 x 100 x 200, and the number of protrusions of 1 μm to 2 μm is read from the chart.

〔Effect of the invention〕

As is clear from the results shown in Table 1, when the back layer according to the present invention is provided, a magnetic recording medium having excellent running durability and winding characteristics as well as excellent magnetic properties (C3/N) can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing an example of an apparatus for testing running durability of a magnetic recording medium. 1... Tape 2... SUS pole No.
1 Amendment to Figure Procedures May 20, 1986

Claims (1)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer in which fine ferromagnetic powder is dispersed on one surface of a non-magnetic support and a back layer on the other surface, the thickness of the back layer is 2.5 μm or less. and the average particle size is 1 μm to 3 μm in the back layer.
m non-magnetic powder on the back layer surface at a height of 1 μm to 2 μm.
A magnetic recording medium comprising 30 to 200 protrusions/mm^2 formed therein.