JPH05174363A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium in which a magnetic layer is hard to be worn and is superior in the durability for environmental change. CONSTITUTION:In the magnetic recording medium in which the magnetic layer containing magnetic powder and a binder is provided on a substrate, the magnetic layer is characterized by incorporating the components described hereunder; (1), (2) and (3). (1) Carbon black with 25-130nm of the average single particle diameter and 300-550ml oil absorption/100g carbon black. (2) Carbon black with 300-1000nm of the average single particle diameter. (3) At least one kind selected from higher fatty acids and fatty acid esters having <=30 deg.C melting point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having excellent durability.

[0002]

2. Description of the Related Art A magnetic recording medium is generally composed of a magnetic film, a binder resin (binder), an organic solvent and other necessary components on a non-magnetic support such as a polyester film. Although it is made by applying paint, the floppy disk, in particular, is in strong contact with the magnetic head, jacket liner, etc. during recording and reproduction, so the magnetic layer is easily abraded, so the magnetic layer is less likely to wear and has excellent durability. What is required is required.

Therefore, as one measure for improving the wear resistance of the magnetic layer, various lubricants are mixed in the magnetic layer. Lubricants that have been conventionally used include, for example, fatty acids, fatty acid esters, fatty acid amides,
There are lubricants such as liquid paraffin and wax.

However, these lubricants are not sufficient in terms of performance, particularly durability.

Further, recently, the opportunities for using magnetic recording media under various environments have been increasing, and therefore there has been a strong demand for the development of magnetic recording media having excellent durability against environmental changes. ..

Therefore, an object of the present invention is to provide a magnetic recording medium in which the magnetic layer is hard to be worn and which is excellent in durability against environmental changes.

[0007]

Means for Solving the Problems As a result of intensive studies by the present inventors, in a magnetic recording medium in which a magnetic layer containing magnetic powder and a binder is provided on a substrate, the above magnetic layer comprises the following component (1). The present invention has been completed by finding that a magnetic recording medium characterized by containing (2) and (3) can achieve the above object. (1) Carbon black having an average single particle diameter of 25 to 130 nm and an oil absorption of 300 to 550 ml / 100 g. (2) Carbon black having an average single particle size of 300 to 1000 nm. (3) At least one selected from higher fatty acids and fatty acid esters having a melting point (mp) of 30 ° C. or lower.

The magnetic recording medium of the present invention will be described in detail below.

The carbon black which is the component (1) used in the magnetic layer of the magnetic recording medium of the present invention has an average single particle size of 25 to 130 nm.

The carbon black as the component (1) has an oil absorption of 300 to 550 ml / 100 g.

The amount of carbon black used as the component (1) is preferably 0.5 to 20 parts by weight, more preferably 2 to 15 parts by weight, based on 100 parts by weight of the magnetic powder.

The carbon black which is the component (2) used in the magnetic layer of the magnetic recording medium of the present invention has an average single particle size of 300 to 1000 nm.

The amount of carbon black used as the component (2) is preferably 0.5 to 20 parts by weight, more preferably 2 to 15 parts by weight, based on 100 parts by weight of the magnetic powder. The use ratio of the carbon black as the above-mentioned component (1) and component (2) is (the former) / (the latter) = 30 /
The range of 70 to 70/30 is preferable, and
The total amount of both used is 100 parts by weight of the magnetic powder,
It is preferably 20 parts by weight or less.

The higher fatty acid which is the component (3) used in the magnetic layer of the magnetic recording medium of the present invention is lauric acid,
Examples thereof include oleic acid, linolenic acid, linoleic acid, branched myristic acid and branched stearic acid.

The fatty acid ester which is the component (3) used in the magnetic layer of the magnetic recording medium of the present invention is oleyl oleate, a higher fatty acid ester salt of a branched alcohol having 12 or more carbon atoms (tridecyl stearate, 2-decyl tetradecyl oleate, etc.) and the like.

The higher fatty acid or fatty acid ester, which is the component (3), has a melting point of 30 ° C. or lower.

The amount of the higher fatty acid or fatty acid ester used as the component (3) is 100 parts by weight of the magnetic powder.
Preferably 0.5 to 20 parts by weight, more preferably 2 to
15 parts by weight.

The components (1) to (3) may be contained in the magnetic layer by a conventional method, but from the viewpoint of durability durability, the component (1) and / or the component (2). It is preferable that the carbon black as a component is treated with the component (3) and then added.

As the above-mentioned treatment method, for example, the component (1) and / or the component (2) and the component (3) are placed in an inert organic solvent (toluene, xylene, etc.) and the mixture is allowed to stand at room temperature or Examples thereof include a method of stirring under heating.

The magnetic powder used in the magnetic recording medium of the present invention is, for example, acicular fine γ-Fe ₂ O ₃ or Fe ₃ O.
₄ , metal oxides such as CrO ₂ , also Co-deposited γ-Fe ₂ O ₃ ,
Co-doped γ-Fe ₂ O was subjected to processing such as ₃ γ-Fe ₂ O
₃ , iron metal powder, barium ferrite in the form of microplate, and magnetic powder in which some of Fe atoms thereof are replaced with one or more of Ti, Co, Zn, V, Nb, Co, Fe-Co, Examples include ultrafine powder of a metal such as Fe-Ni or an alloy. Of these, iron metal powder has particularly poor chemical stability, and nickel, cobalt, titanium, silicon, aluminum, etc. are added in small amounts in the form of metal atoms, salts, and oxides or surface-treated for improvement. However, these can also be used. Further, the iron metal powder may form a thin oxide film on the surface in a weak oxidizing atmosphere for stabilization, but the iron metal powder treated in this way can also be used.

As the binder used in the magnetic layer of the magnetic recording medium of the present invention, polyurethane or polyester with or without polarity, polyvinyl chloride with or without polarity, and vinyl chloride-vinyl acetate copolymer are used. Polymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide, polyacrylic acid ester, polymethacrylic acid ester, polyvinyl acetate,
Examples thereof include polyvinyl butyral, vinylidene chloride, vinylidene chloride copolymer, nitrification cotton, maleic acid-modified vinyl chloride-vinyl acetate copolymer, ethyl cellulose and the like. These may be used alone, but are usually used as a mixture of two or more kinds. Further, in order to adjust the hardness of the resin (binder), a plasticizer or a curing agent may be added and used.

The amount of the above-mentioned binder compounded is usually 1
15 to 60 parts by weight is preferable with respect to 00 parts by weight. Even if the binder has the largest binding force, the compounding amount is 1
If the amount is less than 5 parts by weight, the strength of the magnetic coating film tends to be weak, and the adhesive force between the substrate and the magnetic coating film may be insufficient. If the blending amount is more than 60 parts by weight, the concentration of the magnetic powder in the magnetic coating film tends to be low and the reproduction output tends to be lowered, and the coating film characteristics may be deteriorated.

To the magnetic layer of the magnetic recording medium of the present invention, in addition to the above-mentioned essential components, additives such as abrasives and antistatic agents usually used in this field can be added, if necessary.

Further, as the non-magnetic support which is a base for producing the magnetic recording medium of the present invention, polyester such as polyethylene terephthalate; polyolefin such as polyethylene and polypropylene; cellulose derivative such as cellulose triacetate and cellulose diacetate. ;
Polycarbonate; polyvinyl chloride; polyimide; plastics such as aromatic polyamide; metals such as Al and Cu; paper and the like are used, and examples of such forms include films, tapes, sheets, disks, cards, drums, and the like. Can be mentioned. The surface of the non-magnetic support may be treated with corona discharge, radiation, ultraviolet rays, or the like, or may be precoated with a suitable resin.

The magnetic recording medium of the present invention is similar to the magnetic layer in an ordinary magnetic recording medium, and carbon black as the component (1) and component (2), and higher fatty acid or fatty acid ester as the component (3). , The above magnetic powder,
It is manufactured by providing the above-mentioned magnetic layer comprising the above-mentioned binder and, if necessary, an additive, on the above-mentioned non-magnetic support serving as a substrate.

[0026]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In each of the following examples,
"Parts" and "%" are based on weight unless otherwise specified.

Example 1 (Composition) Magnetic powder (Co-deposited γ-Fe ₂ O ₃ ) ^{* 4} 100 parts Vinyl chloride-vinyl acetate copolymer ^{* 2} 10 Polyurethane resin ^{* 3} 15 Alumina (average particle size 0.6 μm) ) 10 Carbon black with an average single particle size of 350 nm ^{* 1} 8 Carbon black with an oil absorption of 500 ml / 100g and an average single particle size of 38 nm 8 Oleyl oleate ^{* 1} 10 Toluene 70 Methyl ethyl ketone 70 Cyclohexanone 110 Note) * 1: In advance Oleyl Treated with oleate. In addition, this treatment was carried out by adding this carbon black 8 in toluene.
Part and this oleyl oleate 10 parts, 70-8
It was heated to 0 ° C. and stirred for about 60 minutes. * 2: Trade name VAGH manufactured by Union Carbide * 3: Trade name N-2304 manufactured by Nippon Polyurethane Industry Co., Ltd. * 4: Specific surface area 20 m ² / g

The composition of the above (composition) was 1
Knead for 0 hours, take out through a filter, and immediately before coating, hardener (Coronate made by Nippon Polyurethane Industry Co., Ltd.)
Was added and stirred to obtain a paint. Using an applicator, the obtained coating composition was applied on a polyethylene terephthalate film having a thickness of 75 μm so that the dry film thickness was 1.5 μm, and after drying, calendering was performed to obtain a disc-shaped magnetic disk. It was The obtained magnetic disk was put in a case to make a floppy disk.

The prepared floppy disk was measured with a dynamic friction coefficient measuring device at 60 ° C./25% RH to give a value of 0.
5 hours → 0.5 hours at 60 ℃ / 80% RH, →
Hold at 60 ° C / 80% RH for 2 hours → over 0.5 hours 6
The dynamic friction coefficient was determined in a test environment of 0 ° C./25% RH cycle. Further, the change with time of the dynamic friction coefficient at low temperature (5 ° C./50% RH) was also obtained. The results are shown in Table 1 below.

Example 2 In the composition of Example 1, the magnetic powder was replaced by 100 parts of metal powder (specific surface area 55 m ² / g), and instead of the vinyl chloride-vinyl acetate copolymer and polyurethane resin as the binder. , 12.5 parts of a sodium sulfonate group-containing polyurethane resin (UR-8300 manufactured by Toyobo) and 12.5 parts of a sodium sulfonate group-containing polyvinyl chloride resin (MR-110 manufactured by Nippon Zeon) were used, and oleyl oleate was used. 2-decyl tetradecyl oleate 10 instead of
A floppy disk was prepared in the same manner as in Example 1, except that the same composition as in Example 1 was used except that the parts were used.

For the prepared floppy disk, the dynamic friction coefficient was determined in the same manner as in Example 1. The results are shown in Table 1 below.

Example 3 In the composition of Example 1, the magnetic powder was barium ferrite powder (plate ratio 1: 5, Hc = 720 Oe) 100
In place of the vinyl chloride-vinyl acetate copolymer and the polyurethane resin, the same binder as in Example 2 was used, and oleic acid / oleyl oleate = 1/4 (instead of oleyl oleate). Example 1 using the same composition as in Example 1 except that the (weight ratio) mixture was used.
I made a floppy disk in the same way.

For the prepared floppy disk, the dynamic friction coefficient was determined in the same manner as in Example 1. The results are shown in Table 1 below.

Example 4 As Example 2 except that in the composition of Example 2 10 parts of a mixture of tridecyl stearate / oleyl oleate = 1/1 was used instead of 2-decyl tetradecyl oleate. A floppy disk was prepared in the same manner as in Example 1 using the same composition.

With respect to the prepared floppy disk, the coefficient of dynamic friction was determined in the same manner as in Example 1. The results are shown in Table 1 below.

Comparative Example 1 In the composition of Example 1, the oil absorption was 500 ml / 100.
Oil absorption 125ml / 1 instead of g carbon black
A floppy disk was prepared in the same manner as in Example 1, except that 8 parts of carbon black having a specific surface area of 49 m ² / g was used.

For the prepared floppy disk, the dynamic friction coefficient was determined in the same manner as in Example 1. The results are shown in Table 1 below.

Comparative Example 2 The same composition as in Example 1 was used, except that 10 parts of stearic acid (mp 72 ° C.) was used in place of oleyl oleate in the composition of Example 1. I made a floppy disk.

With respect to the prepared floppy disk, the dynamic friction coefficient was determined in the same manner as in Example 1. The results are shown in Table 1 below.

[0040]

[Table 1]

From the results of the above [Table 1], (1) of the present invention
A floppy disk using a carbon black having a smaller oil absorption amount in place of the component (Comparative Example 1) and a floppy disk using a fatty acid having a higher mp in place of the component (3) of the present invention had a dynamic friction coefficient of The magnetic recording medium of the present invention became significantly larger after 100 minutes or 200 minutes than immediately after the start of the measurement. In the case of, even if there is almost no change in the dynamic friction coefficient with time, the lubricity is good, and the durability is greatly improved, by using a specific carbon black in combination with a specific higher fatty acid or fatty acid ester, even under environmental changes It can be seen that it was possible to obtain a magnetic recording medium having excellent durability.

[0042]

According to the magnetic recording medium of the present invention, the magnetic layer is not easily worn and has excellent durability against environmental changes.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a magnetic powder and a binder provided on a substrate, wherein the magnetic layer contains the following components (1), (2) and (3). Magnetic recording medium. (1) Carbon black having an average single particle size of 25 to 130 nm and an oil absorption of 300 to 550 ml / 100 g. (2) Carbon black having an average single particle diameter of 300 to 1000 nm. (3) At least one selected from higher fatty acids and fatty acid esters having a melting point (mp) of 30 ° C. or lower.