JPS6247820A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a total output characteristic and to decrease output fluctuation by forming a magnetic layer into two-layer constitution for which magnetic powders having different coercive forces are used. CONSTITUTION:The magnetic powder is subjected to a surface treatment by using a silane compd. and titanium compd. having an alkoxy silane group or alkoxy titanium group and primary or secondary hydroxyl group to adjust the coercive force to 350-500Oe. The lower magnetic layer is formed on a substrate by using such magnetic powder as an essential component. The upper magnetic layer is then formed by using the magnetic powder having 600-750Oe coercive force as the essential component. Co-deposited gamma-Fe2O3, etc. is used as the magnetic powder. The magnetic recording medium formed with such magnetic layers has large output, small output fluctuation and excellent performance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media. In particular, 2tLD (Double 5ided, High
density.

This invention relates to a double truck type floppy disk.

[Conventional technology and problems]

Conventionally, in coated magnetic recording media, those in which a magnetic layer is formed by coating one type of magnetic paint on a substrate have been widely used in practical use. There are various physical properties required of magnetic recording media, and output characteristics are one of them.

On the other hand, in recent years, expectations have increased for magnetic recording media that enable higher density recording. Regarding floppy disks, the nominal storage capacity is currently 1000K.
Byte's so-called 21 (D type) has also become commercially available. This 2) ID type has 96 tracks per inch on a 5.25 inch disc. The magnetic powder used in this disk has coercive force (Hc
) is 600 to 750 Oe of Co-coated 7-Fe2O2.

In order to obtain a large reproduction output, it is necessary to increase the content of magnetic powder in the magnetic layer, but for this purpose, it is necessary to minimize the amount of binder resin and to improve the dispersibility of magnetic powder in the magnetic paint. It has to be in good condition. It is also necessary to prepare the magnetic paint so that the packing density of the magnetic powder increases when the solvent evaporates after the magnetic paint is applied.

In order to prepare such a magnetic paint, the optimum formulation must be determined by various combinations of the types and amounts of each component of the magnetic paint. However, it is currently difficult to say that even magnetic recording media manufactured using magnetic coating materials prepared in this manner are satisfactory in terms of total output characteristics.

[Means for solving problems]

As a result of intensive research, the inventors of the present invention have found that the total output characteristics have been greatly improved, especially when using a 21 (D type) floppy disk, the output of 2F is large, the output fluctuation is small, and the balance is good. A magnetic recording medium having such output characteristics was discovered, and the present invention was completed.

That is, the present invention provides a magnetic recording medium in which a magnetic layer is formed on a nonmagnetic substrate, in which the magnetic layer (i) has an alkoxysilane group and a primary or secondary hydroxyl group in the molecule. Coercive force surface-treated with one or more compounds selected from the group consisting of a silane compound and (ii) a titanium compound having an alkoxytitanium group and a primary or secondary hydroxyl group in the molecule. The present invention provides a magnetic recording medium comprising a lower magnetic layer containing magnetic powder with a coercive force of 600 to 750 Oe and an upper magnetic layer containing magnetic powder with a coercive force of 600 to 750 Oe.

The magnetic recording medium of the present invention shows remarkable improvement in output characteristics, especially when used as a 211D type floppy disk.

Various types of magnetic powder with a coercive force of 350 to 500 Oe and a magnetic powder with a coercive force of 600 to 750 Oe can be considered according to the present invention, but in particular Co-coated-Fe20. is preferred.

The lower magnetic layer of the magnetic recording medium of the present invention contains magnetic powder having a coercive force of 350 to 500 Oe and surface-treated with one or more compounds selected from the group consisting of (i) and (11). It will be done. In addition, the upper magnetic layer has a coercive force of 600~
Contains 750 Oe of magnetic powder, which is as described above (
The surface may or may not be treated with one or more compounds selected from the group consisting of i) and (ii).

Examples of the above-mentioned compound (1) according to the present invention include a reaction product of an alkoxysilane coupling agent having a functional group, for example, a compound represented by the following formula and dialkanolamines such as jetanolamine. I can do it.

Specifically, a silane coupling agent represented by the following reaction formula (hereinafter abbreviated as silane coupling agent 1) is exemplified.

Examples of the compound (ii) include a compound represented by the following formula % (hereinafter abbreviated as titanium coupling agent 1).

As the binder resin that can be used in the magnetic recording medium of the present invention, commonly used binder resins can be used, such as plasticized vinyl chloride/vinyl acetate copolymer resin, vinyl chloride/vinyl acetate copolymer resin, Polyvinyl chloride resin, polyurethane resin, epoxy resin, polyester resin, polyacrylonitrile resin, nitrile rubber, polyamide resin, polyacrylic acid ester, polymethacrylic acid ester, polyvinylidene chloride, copolymer based on vinylidene chloride, nitrification Examples include cotton, cellulose acetate butyrate resin, and the like. Among these binder resins, polyurethane resins, polyester resins, polyacrylonitrile resins, and polyamide resins are preferable for the lower magnetic layer, and vinyl chloride/vinyl acetate copolymer resins, polyurethane resins, and polyamide resins are preferable for the upper magnetic layer. Acrylonitrile resin, nitrified cotton, and cellulose acetate butyrate resin are preferred.

These binder resins may be used alone or in combination of two or more.

In the present invention, there are several possible methods for obtaining the surface-treated magnetic powder, but as a simple and reliable method, a predetermined amount of one or more selected from the group consisting of (1) and (ii) above can be used. This method involves dissolving the compound in water or an organic solvent, adding magnetic powder to the solution, and stirring while heating if necessary. Then, the solvent is removed and the powder is dried to obtain a surface-treated powder. The amount of the compound used in the surface treatment is 0.5 to 15% by weight, preferably 1% by weight of the magnetic powder.
~8% by weight.

The lower N magnetic layer of the magnetic recording medium of the present invention usually contains a polyisocyanate compound as a coating hardness modifier. Examples of the polyisocyanate compound include a reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate (Coronate L manufactured by Nippon Polyurethane Industries, Sumidur manufactured by Sumitomo Bayer), 1 mol of water, The reaction product of 3 mol of hexamethylene diisocyanate (Sumidur N-3200 manufactured by Bayer Bayer ■), the reaction product of 1 mol of isocyanurate and 3 mol of hexamethylene diisocyanate (Sumidur N-3200 manufactured by Bayer Bayer ■) -3300), etc. The amount of these polyisocyanate compounds used is 5 to 25% by weight, preferably 7 to 15% by weight, based on the total amount of the binder. If the amount used is less than 5% by weight, uneven swelling or dissolution tends to occur when coating the upper magnetic layer, and if it exceeds 25% by weight, the coating film tends to become brittle. These polyisocyanate compounds are
It may or may not be contained in the upper magnetic layer of the magnetic recording medium of the present invention.

The specific method for manufacturing the magnetic recording medium of the present invention will be described in the following examples, but the outline will be as follows: Predetermined magnetic powder, binder resin, solvent, and other additives (abrasives, lubricants,
41) An antistatic agent, etc.) is kneaded into a paint and coated on the substrate, followed by drying, calendering, and curing.

The various additives described above are added to either the lower magnetic layer or the upper magnetic layer, or both.

〔Example〕

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

Example 1 First, Co deposition r-Fe203 (Ilc:430O
e) was suspended in toluene, 4% by weight of the titanium coupling agent 1 was added to the magnetic powder, and 9 was added with stirring.
It was kept at 0°C for 2 hours. Thereafter, the system was cooled to room temperature, toluene was removed by centrifugation, and the system was dried to obtain surface-treated magnetic powder.

Next, a paint for the lower magnetic layer having the following composition was prepared by kneading in a sand mill for 4 hours.

Surface treatment Co-adhered T -Fe203 103 Polyester lower polyester resin 0165 Butyl stearate 5 Polyisocyanate compound 29 Solvent 13 Suitable Note) 4 Product name Byron 200. Toyobo (Reproduction *2 Product name Coronate!
21st, Wood Polyurethane Industries (Co., Ltd. Bookbinding 3 Methyl Ethyl Ketone Amount Ratio) This magnetic paint was coated on a polyester film with a thickness of 75 mm so that the dry film thickness was 0.3-, and heated at 110°C.
The lower magnetic layer was formed by curing for 14 seconds during drying.

Next, apply the paint for the lower magnetic layer with the following composition using a sand mill.
Manufactured by kneading for hours.

Co adhesion r -Fe203 (Hc:660Oe)
100 parts by weight PVC/vinyl acetate copolymer resin” 25
Polyurethane resin 225 Oleic acid 2-butyl stearate 4 Carbon blank 14 α-alumina powder 5 Polyisocyanate compound 47 Capacity: 1m5
Suitable note) Book 1 Product name VAGI! , Union Carbide Co., Ltd. Binding 2 Product name N-2301, Nippon Polyurethane Co., Ltd. Production rate 3 Product name Ketjen Black, Lion Akzo Co., Ltd. *44 Double name Coronae 1-1 Nippon Polyurethane Co., Ltd. 0 Binding 5 Methyl ethyl ketone amount ratio This magnetism The paint was applied onto the lower magnetic layer so that the dry film thickness was 1.0 mm, cured for 8 seconds in a drying oven at 110°C, and then cured at 50°C for 3 days. Thereafter, it was punched out into a disk shape with a diameter of 5.25 inches, the surface was polished with an abrasive tape, and the disk was placed in a salmon throat to make a floppy disk.

Next, we determined the high frequency output toughness (2) of this floppy disk.
The output of 2F at 50 KIlz and the output fluctuation of the innermost track) were measured using a commercially available floppy disk drive. The results are shown in Table 1.

Example 2 First, Co-coated r-FezOx (Hc: 430 Oe
) was suspended in toluene, 3.5% by weight of the silane coupling agent 1 was added to the magnetic powder, and the method of Example 1 was followed to obtain a surface-treated magnetic powder.

Next, the coating material for the lower magnetic layer shown in Example 1 was produced using 103 parts by weight of the surface-treated Co magnetizable powder obtained by Koko. Then, according to the method of Example 1, a lower magnetic layer was formed.

Next, a magnetic paint for the upper layer having the composition shown in Example 1 was manufactured according to the method of Example 1, and it was coated on the lower magnetic layer, punched out into a disk shape, put in a jacket, and used as a floppy disk. And so.

The performance of this floppy disk was measured according to the method of Example 1. The results are shown in Table 1.

Comparative Example 1 Instead of the surface-treated Co-coated r-Fe203 used in Example 1, Co-coated 'r-FezO without surface treatment was used.
A coating material for the lower magnetic layer was prepared by using Z and triple oleic acid as a dispersant, and a floppy disk was obtained according to the method of Example 1. The performance of this floppy disk was measured according to the method of Example 1.

The results are shown in Table 1.

Table 1 As is clear from Table 1, the magnetic recording medium of the present invention has a large output, small output fluctuation, and has excellent performance.

Claims (1)

[Claims] 1. In a magnetic recording medium formed by forming a magnetic layer on a non-magnetic substrate, the magnetic layer includes (i) an alkoxysilane group and a primary or secondary alkoxysilane group in the molecule;
one or more compounds selected from the group consisting of a silane compound having a class hydroxyl group, and (ii) a titanium compound having an alkoxytitanium group and a primary or secondary hydroxyl group in the molecule. A magnetic recording medium comprising a lower magnetic layer containing surface-treated magnetic powder with a coercive force of 350 to 500 Oe and an upper magnetic layer containing magnetic powder with a coercive force of 600 to 750 Oe.