JPH03286422A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having excellent magnetic powder dispersibility, surface smoothness and electromagnetic conversion characteristics by incorporating a specific quaternary ammonium salt and magnetic powder of <=7pH into a magnetic layer. CONSTITUTION:The quaternary ammonium salt expressed by formula I and the magnetic powder of <=7pH are incorporated into the magnetic layer. In the formula I, at least either of R1, R2 is 8 to 22C alkyl group and the other is 1 to 20C alkyl group; X denotes a halogen atom. The quaternary ammonium salt expressed by the formula I is added at 0.5 to 10pts.wt., more preferably 1 to 4pts.wt. per 100pts.wt. magnetic powder. The magnetic powder of <=7pH is exemplified by barium ferrite (Ba-Fe), gamma-Fe2O3, etc., of planar crystals. The magnetic recording medium having the excellent magnetic powder dispersibility, surface smoothness and electromagnetic conversion characteristics is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having excellent magnetic powder dispersibility, surface smoothness, and electromagnetic conversion characteristics.

[Prior Art and Problems to be Solved by the Invention] Magnetic powder in magnetic recording media such as magnetic tapes and magnetic disks is required to have a high degree of dispersibility.

Magnetic recording media are generally manufactured by kneading magnetic powder, binder, various additives, and solvents, and then uniformly applying a magnetic paint onto a substrate such as a plastic film or sheet and drying it, and then polishing the magnetic layer to a mirror-like surface. Although it is formed by finishing, it is not possible to create a uniform and smooth magnetic layer with a high packing density unless the magnetic powder in the magnetic paint is sufficiently dispersed and peptized to remove aggregated particles.

Non-uniformity of the magnetic layer due to agglomerated particles of magnetic powder has a serious adverse effect on the electromagnetic conversion characteristics and magnetic properties of the magnetic tape. That is, it causes a decrease in output, an increase in noise, dropouts, etc. Additionally, if the adhesive force between the magnetic powder and the binder is weak, the magnetic powder may peel off from the magnetic coating layer (so-called "powder shedding") when the magnetic recording medium and the recording head or reproduction head slide. This easily occurs, and the coating surface becomes rough, impairing the durability of the magnetic recording medium.

In addition, in recent years, especially from the perspective of high-density recording in magnetic recording media, plate-shaped barium ferrite powder and iron powder have been used in addition to the conventionally used iron oxide-based ferromagnetic powder. It is important to disperse the particles more uniformly in the layer, and currently there is a need for dispersants, magnetic powder surface treatment agents, dispersion techniques, etc. for this purpose.

[Means to solve the problem]

As a result of intensive research into improving the dispersibility of magnetic powders with a pH of 7 or less, such as barium ferrite, the present inventors found that by adding a specific quaternary ammonium salt to magnetic paint raw materials, excellent magnetic properties could be achieved. Powder dispersibility, surface smoothness,
It was discovered that a magnetic recording medium having electromagnetic conversion characteristics can be obtained, and the present invention was completed.

That is, the present invention provides a magnetic recording medium in which a magnetic layer is coated on a non-magnetic support, in which the magnetic layer contains the following general formula (1) [wherein RI+R2' at least one has 8 to 22 carbon atoms] One is an alkyl group, and the other is an alkyl group having 1 to 20 carbon atoms.

X: means a halogen atom. ] A magnetic recording medium characterized by containing a quaternary ammonium salt represented by the following and a magnetic powder having a pH of 7 or less is provided.

The quaternary ammonium salt represented by the above general formula (1) used in the present invention is 0.5 to 0.5 parts by weight per 100 parts by weight of magnetic powder.
It is added in an amount of 10 parts by weight, preferably 1 to 4 parts by weight. Fourth
If the amount of the grade ammonium salt added is less than 0.5 parts by weight, no effect will be exhibited, and if it exceeds 10 parts by weight, it will tend to bleed from the magnetic layer and contaminate the magnetic head during the magnetic recording and reproducing process, so it is preferable. do not have.

Magnetic powders with a pH of 7 or less used in the present invention include plate-shaped barium ferrite (Ba-Fe), 7-Fe4
0= etc. are mentioned.

The binder used in the magnetic recording medium of the present invention includes polyurethane, polyester, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide. , polyacrylic acid ester, polymethacrylic acid ester, polyvinyl acetate, polyvinyl butyral, vinylidene chloride, vinylidene chloride copolymer, nitrified cotton, maleic acid-modified vinyl chloride/vinyl acetate copolymer, and ethyl cellulose. These may be used alone or in combination of two or more. Further, in order to adjust the hardness of the resin, a plasticizer or a hardening agent may be added.

Further, the amount of the binder blended is generally 15 to 60 parts by weight per 100 parts by weight of the magnetic powder.

In addition to the above-mentioned components, additives such as lubricants, abrasives, and antistatic agents commonly used in this field can be added to the magnetic layer of the magnetic recording medium of the present invention.

In addition, non-magnetic supports used in manufacturing the magnetic recording medium of the present invention include polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; Vinyl chloride; polyimide; plastics such as aromatic polyamide; metals such as Al and Cu; and the like are used. The form may be a film, tape, sheet, disk, card, drum, etc. Further, the surface of the support may be treated with corona discharge, radiation, ultraviolet light, etc., or may be precoated with a suitable resin.

〔Example〕

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 The blended composition shown in Table 1 was kneaded in a ball mill for 72 hours, and 8 parts by weight of Coronet) L (trade name 5, a polyisocyanate compound manufactured by Nippon Polyurethane Industries) was added as a hardening agent.
It is coated on a polyethylene terephthalate film having a thickness of 75 Ifm so that the dry film thickness is 2.5 -, and after drying, it is calendered and punched out into a disk shape to obtain a magnetic disk.

The reflectance (Gloss) and center line average roughness (Ra) of the magnetic disk were measured. Furthermore, this was enclosed in a jacket and the C/N ratio near 7 MHz was measured.

The results are shown in Table 2.

Example 2 Alucard 2TH-75J (R3=R in general formula (1)
Implemented except that z = mixture of C1g alkyl group and R1 = RZ = CI6 alkyl group, X = CI) and alcohol copolymer (trade name rVAGl (manufactured by J Union Carbai Co., Ltd.) was used instead of nitrocellulose. A magnetic disk was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

The results are shown in Table 2.

Example 3 Alucard 18-75J (R+=C in general formula (1)
A magnetic disk was prepared in the same manner as in Example 1, except that H1Rz=C+a a mixture of alkyl groups and CI6 alkyl groups, X=CI), and the same evaluation as in Example 1 was performed.

The results are shown in Table 2.

Comparative Example 1 The same procedure was carried out except that a phosphoric acid ester compound (trade name: rGafacRE 610J manufactured by Toho Chemical Co., Ltd.) was used in place of Alucard 2C-75J of the quaternary ammonium salt of the blended composition in Table 1 used in Example 1. A magnetic disk was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

The results are shown in Table 2.

Comparative Example 2 N-alkyl trimethylene diamine dioleate (trade name "Duomin" manufactured by Lion Akzo Co., Ltd.) was used instead of "Alucard 2C-75J" of the quaternary ammonium salt of the blended composition in Table 1 used in Example 1. ) Example 1 except that
A magnetic disk was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

The results are shown in Table 2.

Table 1 Magnetic paint composition Note) *1 Magnetic powder: Ba-Fe powder with pH 6.5, specific surface area 30 bo/g, plate ratio 1:5 *2 Quaternary ammonium salt: Product name "Alucard 2C-75J ( Made by Lion ■
R + = Rz = C+ z in general formula (1)
.

*3 *4 Book 5 *6 CI41 A mixture mainly composed of C161cle, X =
CI) Polyurethane resin: Product name: Niraporan N-2300J (manufactured by Nippon Polyurethane Kogyo Co., Ltd.) Nitrocellulose: Product name: Seltsuba BTK 1/8J (manufactured by Asahi Kakai Kogyo Co., Ltd.) Carbon black: Specific surface area 950 n'r/g, average Single particle size: 17 kaalumina: Average particle size: 0.6μ The magnetic layer peeled off during measurement, so measurement could not be performed.

Table 2

Claims (1)

[Claims] In a magnetic recording medium comprising a magnetic layer coated on a non-magnetic support, the magnetic layer contains the following general formula (1) ▲mathematical formula, chemical formula, table, etc.▼(1) In the formula, R_1, R_2: at least one is an alkyl group having 8 to 22 carbon atoms, and the other is an alkyl group having 1 to 20 carbon atoms. X: means a halogen atom. ] A magnetic recording medium characterized by containing a quaternary ammonium salt represented by the following and a magnetic powder having a pH of 7 or less.