KR930000442B1 - Magnetic medium - Google Patents

Abstract

No content.

Description

Magnetic recording medium

The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium such as a magnetic tape suitable for audio recording or video recording.

In general, a magnetic recording medium is produced by applying a magnetic coating comprising a magnetic powder binder component, an organic solvent and other necessary components on a substrate such as a polyester film and drying it.

In this case, as the binder component to be used, it is necessary to select a magnetic powder having excellent dispersibility and good surface smoothness of the magnetic layer to impart high sensitivity and high SN boiling to the magnetic recording medium, and at the same time, excellent wear resistance. There is.

Among the binder resins currently used, nitrocellulose is known to have relatively good characteristics, but not enough. Particularly, when using a magnetic powder having an active surface such as a metallic magnetic powder, a part of the nitrocellulose reacts with the metallic magnetic powder surface. There is a tendency to gel, so that it is very difficult to disperse the magnetic powder well and it is still not possible to sufficiently disperse the powder.

MEANS TO SOLVE THE PROBLEM As a result of carrying out various examinations in order to improve this fault, when using the low molecular weight nitrocellulose whose weight average molecular weight is 40,000 or less, a magnetic coating does not gelatinize and it does not become a conventional relatively high molecular weight nitrocellulose. On the other hand, it was found that the dispersibility of the magnetic powder was further improved, but the abrasion resistance was not very good. As a result of continuing the examination, the nitrocellulose having a weight average molecular weight of 40,000 or less was selected from the group consisting of polyurethane resins, acrylonitrile butadiene copolymer resins, rubber chlorides, polyester resins, polyamide resins, epoxy resins, and vinyl chloride resins. When used in combination with at least one selected from the group, the dispersibility of the magnetic powder is sufficiently improved, the surface smoothness of the magnetic layer is improved, and the wear resistance of the magnetic layer is also improved, thereby finding a magnetic recording medium having excellent electrical characteristics and durability. Was done.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a magnetic recording medium having a magnetic layer having excellent dispersibility of magnetic powder and excellent wear resistance.

In the present invention, the nitrocellulose used is a low molecular weight nitrocellulose having a weight average molecular weight of 40,000 or less. If the weight average molecular weight is larger than this, when the magnetic coating is prepared by mixing with a magnetic powder, the magnetic coating becomes high viscosity. Although it may gel, this kind of low molecular weight nitrocellulose does not have this kind of thing, and affinity with magnetic powder is also favorable, and the dispersibility of magnetic powder is improved. As a result, the surface smoothness of the magnetic layer is also good, and the magnetic properties and the electromagnetic conversion properties are sufficiently improved.

As such nitrocellulose, those having a weight average molecular weight of less than 40,000 are preferable, but those having a weight average molecular weight of less than 30,000 are more preferably used, and specific examples thereof include, for example, Nitrocellulose Cellulon EX-2 manufactured by Asahi Kasei, Japan. Can be mentioned.

In addition, all of the polyurethane-based resin, acrylonitrile butadiene copolymer-based resin, rubber chloride, polyester water, polyamide resin, epoxy resin, and vinyl chloride resin used together have excellent toughness, and the weight average molecular weight described above. The compatibility with the nitrocellulose of 40,000 or less is also good, and the wear resistance is improved by making the strength of the magnetic layer an appropriate strength. As such a polyurethane-type resin, all the thing from the low molecular weight of 1000-100000 to the high molecular weight are used, As a specific example, Tatenate L-1007, Tatenate L-2710, and Tagelac E which are manufactured by the Japanese Tageda Pharmaceutical Co., Ltd. -551T, Tagerak E-550, Pandex T-5250, Pandex T-5201, Pandex T-5205, etc. which are manufactured by Nippon Ink Chemical Co., Ltd., etc. are mentioned.

More preferably, the polyurethane resin may be a polyurethane resin at the time of forming the magnetic coating. Therefore, from the viewpoint of achieving high dispersion of the magnetic powder and high elasticity of the magnetic layer, the low molecular weight of the magnetic powder and the polyurethane resin raw material It can also be made into a polyurethane resin by carrying out reaction by mixing and disperse | distributing in presence of a polyol, an isocyanate compound, and the said specific fibrin type resin.

At this time, the above-described fibrous resin and polyurethane resin surround the magnetic powder to form a rigid matrix, so that a magnetic layer having a particularly high elastic modulus is obtained, so that a tape requiring high density recording can be thinned and exhibits excellent running performance.

At this time, in order to obtain the elastic modulus of a particularly high coating film, it is necessary to use a low molecular weight polyol, specifically, it is preferable that an average molecular weight is 700 or less and a hydroxyl group is 200 or more in acrylic polyol, polyester polyol, polyether polyol, etc. .

As a specific example of a polyester polyol, Adeka New Ace YT-400 (average molecular weight 400, a hydroxyl value of 580) by the Asahi telephone company of Japan, etc., Sannix TP-400 (Average of Samyang Chemicals, Japan) is mentioned as a specific example of a polyester polyol. Molecular weight 400, hydroxyl value 430), etc. are mentioned. Moreover, as an isocyanic acid compound, 1-methyl benzol-2, 4, 6- triisocyanoic acid, triphenyl methane-4, 4 ', 4 "-triisocyanic acid, trimethyl propane tolylene diisocyanic acid, isophorone Diisocyanic acid, these adducts, etc. are mentioned.

As specific examples, for example, Polyurethane L from Japan Polyurethane Industry Co., Tagenate D102 from Tageda Kogyo Kogyo Kogyo Co., Ltd., Death Module L from Bayer Co., Ltd., Crisbon NX from Nippon Ink Chemical Co., Ltd., Mitek NY from Mitsubishi Chemical Corporation, etc. Can be mentioned.

The ratio of the use of these low molecular weight polyols and polyisocyanate compounds may be set in an appropriate amount such that the magnetic coating film becomes non-adhesive due to the curing reaction between them, and in general, the amount of hydroxyl groups per equivalent of isocyanate groups is preferably 0.8 to 1.2 equivalents. In the weight ratio, the polyol to polyisocyanate compound is preferably about 3/1 to 1/7.

Moreover, an acrylonitrile butadiene copolymer, an acrylonitrile butadiene styrene copolymer, etc. are mentioned as a specific example of acrylonitrile butadiene copolymer system resin.

As a specific example of a commercial item, Nippon 1432J by Xeon Japan, the Tapurex 400 by Mitsubishi Monsant, etc. are mentioned.

Specific examples of the polyester-based resin include Orion Spinning Co., Ltd., Byron # 200, and Japan-Japan Ink Chemical Co., Ltd. (Crisbon 6019), and specific examples of the polyamide-based resin are Zebu Besamide V-125 from Moldy Chemical Co., Ltd. and Elba from Dupont. Eid 8061 etc. are mentioned.

Specific examples of the epoxy resin include Epiclon 800 manufactured by Nippon Ink Chemical Co., Ltd., Eposer W100EL, Adeka Resin EPU-2 manufactured by Asahi Kogyo Co., Ltd., and the like.

Specific examples of the vinyl chloride-based resin include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-vinyl-maleic acid copolymer, vinyl chloride-vinyl propionate copolymer, and the like.

Specific examples of commercially available products include VYHH, VAGH, VMCH, U.C.C., U.C.C., Esrek A, Eclectic Chemicals, Ryuron QS-430, Ryuron QA-431, and the like.

The blending ratio of nitrocellulose with a weight average molecular weight of 40,000 or less, a polyurethane resin, an acrylonitrile butadiene copolymer resin, a rubber chloride, a polyester resin, a polyamide resin, an epoxy resin, and a vinyl chloride resin is The ratio of the former to the latter is preferably in the range of 95 to 25 to 75 in terms of weight ratio. If the electron is too small, the dispersibility of the magnetic powder is not sufficiently improved. There is a time.

In the present invention, the isocyanate compound may be used in combination with the binder resin as described above. When such isocyanate compound is used in combination, the nitrocellulose, the polyurethane-based resin, and the acrylonitrile butadiene copolymer-based resin may be used. Since rubber chloride, polyester resin, polyamide resin, epoxy resin, salt vinyl resin and isocyanate compound crosslink, the strength of the magnetic layer is further strengthened, and the wear resistance of the magnetic layer is further improved. The amount of the binder is preferably used in the range of 1 to 40% by weight based on the total amount of the binder component, and the amount of 1% by weight or less does not sufficiently improve the wear resistance of the magnetic layer. Too many to make the magnetic layer hard and brittle. As such an isocyanate compound, the thing similar to the above can be selected.

As the magnetic powder, for example, r-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing r-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, CrO ₂ powder, Fe powder, Co powder, Fe Although various conventionally known magnetic powders such as -Ni powder are widely included, in particular, when the metal powder is used, a particularly noticeable effect is obtained.

Moreover, as an organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetra hydrofuran, dimethyl formamide, etc. are used individually or in mixture of 2 or more types.

In the magnetic paint, various additives commonly used, for example, a dispersant, a lubricant, an abrasive, an antistatic agent, and the like may be arbitrarily added and used.

In order to manufacture the magnetic recording medium of the present invention, a conventional method may be used. For example, a magnetic powder, a nitrocellulose having a weight average molecular weight of less than 40,000, a polyurethane-based resin, and acrylonitrile butadiene are copolymerized on a substrate such as a polyester film. At least one binder component selected from system resins, rubber chlorides, polyester resins, polyamide resins, epoxy resins, and vinyl chloride resins, or a binder component obtained by adding an isocyanate compound to the organic resin The magnetic paint containing the solvent and other additives may be applied and dried by any means such as paint by adsorption or roll. The nitrocellulose having a weight average molecular weight of 40,000 or less may be contained in the magnetic layer by a method such as surface treatment of the magnetic powder using the same.

Next, the Example of this invention is described.

Example 1

100 parts by weight of α-Fe magnetic powder

Pandex T-5205 18 parts by weight

(Product made in Nippon Ink Chemical Co., Ltd.

Urethane Elastomer

2 parts by weight of nitrocellulose Cellulon EX-2

Asahi Kasei Co., Ltd.

Nitrocellulose)

Coronate L 2 parts by weight

(Product made in Japan polyurethane industry company

Trifunctional low molecular weight isocyanate compounds)

146 parts by weight of ethyl isobutyl ketone

Toluene 73 parts by weight

In this composition, each component except Cononate L was mixed-dispersed in a ball mill for about 72 hours, and after adding and mixing Colonate L for another 1 hour, it was taken out, and a magnetic coating was prepared. This magnetic paint was applied onto a polyester film having a thickness of 10 µm so as to have a dry thickness of 3.5 µm, dried, subjected to surface treatment, and then cut into a predetermined width to form a magnetic tape.

Example 2

The magnetic tape was produced in the same manner as in Example 1 except that Colonate L was omitted in the composition of the magnetic coating of Example 1 and the amount of Pandex T-5205 was changed from 18 parts by weight to 20 parts by weight.

Example 3

Except for changing the usage amount of Pandex T-5205 from 18 parts by weight to 16 parts by weight in the composition of the magnetic coating of Example 1, and changing the usage amount of nitrocellulose cellulose Nov-2 from 2 parts by weight to 4 parts by weight. In the same manner as in Example 1, a magnetic tape was produced.

Example 4

Magnetic iron 500 parts

Low molecular weight fiber resin (10 parts of Asahi Kasei)

Product EX-2

60 parts vinyl chloride-vinyl acetate copolymer

(VAGH made by U.C.C.

11 parts of polyester polyol

29 parts of polyisocyanate compounds

(Death module L-75 from Bayer)

350 parts of methyl isobutyl ketone

Cyclohexanone 350 parts

Toluene 350 parts

Each component except the polyisocyanate compound in the composition was put into a ball mill and dispersed for 48 hours, and then the polyisocyanate compound was added, mixed and dispersed for 1 hour, and then taken out to prepare a magnetic paint.

And, as said polyester polyolol, Adeka New Ace YT-400 (average molecular weight 400, hydroxyl value 580) by Asahi telephone company was used.

The magnetic coating was applied on a 15 μm-thick polyester base so as to have a dry thickness of 5 μm, directed to a direct current magnetic field of 3 k Ersted, heat dried (cured), and calendered. Then, it was cut to 1/2 inch wide to make a video tape.

Example 5

An example was used in place of the polyester polyol, except that 12 parts of a polyester polyol (Sanyang TP-400 manufactured by Samyang Chemical): an average molecular weight of 400 and a hydroxyl value of 430) were used, and the use number of the polyisocyanate compound was 28 parts. Like all 1, I made a videotape.

Example 6

A video tape was produced in the same manner as in Example 1 except that 60 parts of a polyester resin (Dongyang Spinning Company name Byron 300) was used instead of the vinyl chloride-vinyl acetate copolymer.

Comparative Example 1

A magnetic tape was produced in the same manner as in Example 1 except that the same amount of Nitrocellulose H1 / 4 was used in place of the Nitrocellulose Cellulover EX-2 of Example 1.

Comparative Example 2

A magnetic tape was produced in the same manner as in Example 1 except that 12 parts by weight of nitrocellulose H1 / 4 was used instead of the nitrocellulose Cellulon EX-2 of Example 1.

Comparative Example 3

The magnetic tape was produced in the same manner as in Example 4 except that the low molecular weight cellulose resin was omitted in Example 4.

The weight average molecular weight of the nitrocellulose used in each of the Examples and Comparative Examples was measured under the following conditions. As a result, the nitrocellulose Cellulon EX-2 used in the Examples was 23900, nitrocellulose H1 / 4 was 53000, and nitrocellulose H1 / 2 was It was 71000.

(Measurement condition of weight average molecular weight)

Apparatus: Gel Penetration Chromatograph

GPC-244 (WATERS)

Data Processing: TRC GPC Data Processing System

Column: TSK-GEL-GMH ₆ (2)

Solvent: Tetrahydrofuran

Flow rate: 2ml / min

Temperature: 25 ℃

sample

Concentration: 0.2% (wt / vol)

Solubility: Completely Soluble

Filtration: 0.5μ-FHLP FILTER (MILLIPORE)

Injection volume: 0.5ml

Detector: Differential Refractive Index Detector, R-401 (WATER)

Molecular weight calibration: based on POLYSTYRENE

Moreover, the viscosity of the magnetic coating prepared in each Example and each comparison was measured, and also the surface smoothness and the sensitivity of the magnetic layer were measured about the magnetic tape obtained by each Example and each comparative example. And surface smoothness and a sensitivity were measured by the following method.

[Surface Smoothness]

The surface roughness (CLA) of the magnetic layer was measured under the conditions of needle contact speed 0.06 cm / sec and cutting 0.08 mm using a roughness gauge at the time of needle contact, and the relative value calculated according to the following equation based on the example 1 It was judged that the surface smoothness was good or bad.

[Sensitivity]

The output (dB) of 5 MHz of each sample when the thing of Example 1 was made into the reference | standard (0 dB) was calculated | required.

[Elastic Modulus of Magnetic Layer]

While the elastic modulus of the entire tape is measured under conditions of a sample length of 10 cm and a tensile speed of 20 mm / min, the elastic modulus of only the polyester base film is measured, and the elastic modulus of only the magnetic layer is obtained from the measured values according to the following equation.

dM: thickness of magnetic layer (cm)

dB: Thickness of Polyester Base Film (cm)

E _T : Elastic modulus of the whole tape

E _B : Elastic modulus of polyester base film

From the elasticity modulus of the magnetic layer of each sample computed by said formula, the relative value was calculated | required according to the following formula based on the thing of Example 1, and it was determined whether the elasticity modulus of a magnetic layer is large by this relative value.

The results are shown in Table 1 below.

TABLE 1

As can be seen from Table 1, each of the magnetic paints obtained in Examples 1 to 6 of the present invention has increased viscosity, no gelation, and high surface smoothness and sensitivity as compared with Comparative Examples 1 to 3. Therefore, the magnetic recording medium of the present invention has the effect of excellent dispersibility of the magnetic powder and good surface smoothness of the magnetic layer, thereby improving the electromagnetic conversion characteristics.

Claims (3)

A magnetic recording medium provided with a magnetic coating film on which a magnetic powder is dispersed in a binder on a support, wherein a part of the binder contains a fiber-based resin having a weight average molecular weight of 40,000 or less, and the fiber-based resin is nitrocellulose. Magnetic recording medium characterized in that. The method of claim 1, wherein in the remainder of the binder, a polyurethane resin, an acrylonitrile butadiene copolymer resin, a rubber chloride, a polyester resin, a polyamide resin, an epoxy resin, a vinyl chloride resin A magnetic recording medium comprising at least one selected kind to form the magnetic coating film. The method of claim 2, wherein the remainder of the binder is a polyurethane resin, and the polyurethane resin reacts by mixing and dispersing a low molecular weight polyol and an isocyanate compound in the presence of magnetic powder in the magnetic coating film. And a magnetic recording medium.