JP2942650B2 - Magnetic recording media - Google Patents

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 powder, a binder resin, an organic solvent and other necessary components on a non-magnetic support such as a polyester film. The floppy disk is made by applying paint, but the floppy disk is especially hard to wear because the magnetic layer is liable to wear due to heavy contact with the magnetic head and jacket liner during recording / reproduction. Is required.

For this reason, as one measure to improve the wear resistance of the magnetic layer, various lubricants have been mixed into the magnetic layer. Conventionally used lubricants include, for example, fatty acids, fatty acid esters, fatty acid amides,
There are lubricants such as liquid paraffin and wax.

[0004] However, these lubricants are hardly satisfactory in terms of performance, especially in terms of durability.

In recent years, the use of magnetic recording media in various environments has been increasing, and there has been a strong demand for the development of magnetic recording media having excellent durability especially against environmental changes. .

Accordingly, it is an object of the present invention to provide a magnetic recording medium in which the magnetic layer is hardly worn and which has excellent durability against environmental changes.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that in a magnetic recording medium having a magnetic layer containing a magnetic powder and a binder provided on a substrate, the magnetic layer has the following component (1). , (2) and (3) have been found to be able to achieve the above object, and the present invention has been completed. (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 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.

Hereinafter, the magnetic recording medium of the present invention will be described in detail.

The carbon black as 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.

[0010] The carbon black of 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 as 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 usage ratio of the carbon blacks (1) and (2) is (the former) / (the latter) = 30 /
It is preferably in the range of 70 to 70/30,
The total usage of both is based on 100 parts by weight of the magnetic powder,
It is preferable that the content be 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 includes lauric acid,
Oleic acid, linolenic acid, linoleic acid, branched myristic acid, branched stearic acid and the like can be mentioned.

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

The higher fatty acid or fatty acid ester as the component (3) has a melting point of 30 ° C. or less.

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

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

As the above-mentioned treatment method, for example, the component (1) and / or the component (2) and the component (3) are put in an inert organic solvent (toluene, xylene, etc.), A method of stirring under heating and the like can be mentioned.

Examples of the magnetic powder used in the magnetic recording medium of the present invention include fine needle-like γ-Fe ₂ O ₃ and Fe ₃ O
_4, a metal oxide such as CrO _2, also Co-coated 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, microplate-shaped barium ferrite and magnetic powder in which a part of Fe atoms are replaced by one or more of Ti, Co, Zn, V, Nb, etc., Co, Fe-Co, Examples include ultrafine powders of metals or alloys such as Fe-Ni. Of these, iron metal powder has particularly poor chemical stability, and for this improvement, nickel, cobalt, titanium, silicon, aluminum, etc. are added in small amounts in the form of metal atoms, salts, and oxides or surface-treated. However, these can also be used. The above-mentioned iron metal powder may form a thin oxide film on the surface in a weakly oxidizing atmosphere for stabilization, but the iron metal powder treated in this manner may be used.

The binder (binder) used in the magnetic layer of the magnetic recording medium of the present invention may be a polyurethane having a polarity or not, a polyester, a polyvinyl chloride having or not having a polarity, or a vinyl chloride-vinyl acetate. Polymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin, polyamide, polyacrylate, polymethacrylate, polyvinyl acetate,
Examples thereof include 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, but are usually used as a mixture of two or more. Further, in order to adjust the hardness of the resin (binder), a plasticizer or a curing agent may be added for use.

The amount of the binder is usually 1 part of the magnetic powder.
15 to 60 parts by weight is preferable for 00 parts by weight. Even if the binder has the largest binding strength, the amount of compounding is 1
If the amount is less than 5 parts by weight, the strength of the magnetic coating tends to be weak, and the adhesive strength between the substrate and the magnetic coating may be insufficient. If the 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 decrease, and the coating film characteristics may also deteriorate.

The magnetic layer of the magnetic recording medium of the present invention may contain, if necessary, additives such as abrasives and antistatic agents commonly used in this field, in addition to the above essential components.

The non-magnetic support serving as a substrate for producing the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate. ;
Polycarbonate; Polyvinyl chloride; Polyimide; Plastics such as aromatic polyamides; Metals such as Al and Cu; Papers and the like are used. Examples of the form include films, tapes, sheets, disks, cards, and drums. No. The surface of the nonmagnetic support may be treated with corona discharge, radiation, ultraviolet light, or the like, or may be precoated with an appropriate resin.

The magnetic recording medium of the present invention comprises carbon black as component (1) and component (2), higher fatty acid or fatty acid ester as component (3), similarly to the magnetic layer in a normal magnetic recording medium. , The magnetic powder,
It is manufactured by providing the above-mentioned magnetic layer comprising the above-mentioned binder and optionally used additives on the above-mentioned non-magnetic support serving as a substrate.

[0026]

EXAMPLES Hereinafter, the present invention will be described specifically 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-coated 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 ^* 18 carbon black with an oil absorption of 500 ml / 100 g and an average single particle size of 38 nm 8 oleyl oleate ^{* 1} 10 toluene 70 methyl ethyl ketone 70 cyclohexanone 110 Note) * 1: Treated with oleyl oleate. In addition, this treatment is performed by dissolving this carbon black 8 in toluene.
And 10 parts of this oleyl oleate.
The mixture was heated to 0 ° C. and stirred for about 60 minutes. * 2: VAGH brand name manufactured by Union Carbide * 3: N-2304 brand name manufactured by Nippon Polyurethane Industry * 4: Specific surface area 20 m ² / g

The above composition (composition) was mixed with a sand mill to obtain 1
Knead for 0 hour, take out through filter, and just before application, curing agent (Coronatum manufactured by Nippon Polyurethane Industry)
Was added and stirred to obtain a paint. The obtained paint is applied on a 75 μm-thick polyethylene terephthalate film using an applicator so that the dry film thickness becomes 1.5 μm, dried, calendered, and punched into a disk to obtain a magnetic disk. Was. The obtained magnetic disk was put in a case to prepare a floppy disk.

The prepared floppy disk was treated at 60 ° C./25% RH at 0.
5 hours → 0.5 hours to 60 ° C / 80% RH →
Hold at 60 ° C / 80% RH for 2 hours → 6 over 0.5 hours
The dynamic friction coefficient in a test environment of a cycle of 0 ° C./25% RH was determined. Further, the change with time of the dynamic friction coefficient at a low temperature (5 ° C./50% RH) was also determined. 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 a vinyl chloride-vinyl acetate copolymer and a polyurethane resin as a binder, Oleyl oleate using 12.5 parts of a sodium sulfonate-containing polyurethane resin (UR-8300 manufactured by Toyobo Co., Ltd.) and 12.5 parts of a polyvinyl sulfonate-containing polyvinyl chloride resin (MR-110 manufactured by Nippon Zeon) Instead of 2-decyltetradecyl oleate 10
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 for using parts.

The dynamic friction coefficient of the prepared floppy disk 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 replaced by barium ferrite powder (plate ratio 1: 5, Hc = 720 Oe).
In place of the vinyl chloride-vinyl acetate copolymer and the polyurethane resin, the same binder as in Example 2 was used as the binder, and oleic acid / oleyl oleate = 1/4 (instead of oleyl oleate) (Weight ratio) using the same composition as in Example 1 except that the mixture of Example 1 was used.
A floppy disk was created in the same manner as described above.

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

Example 4 The procedure of Example 2 was repeated, except that 10 parts of a mixture of tridecyl stearate / oleyl oleate = 1/1 was used in place of 2-decyltetradecyl oleate. A floppy disk was prepared in the same manner as in Example 1 using the same composition.

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

Comparative Example 1 The composition of Example 1 had an oil absorption of 500 ml / 100.
g of carbon black instead of oil absorption 125ml / 1
A floppy disk was prepared in the same manner as in Example 1 using the same composition as in Example 1 except that 8 parts of 00 g (specific surface area 49 m ² / g) of carbon black was used.

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

Comparative Example 2 The procedure of Example 1 was repeated, except that 10 parts of stearic acid (mp 72 ° C.) was used instead of oleyl oleate. Made a floppy disk.

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

[0040]

[Table 1]

From the results shown in Table 1 above, it is clear that (1) of the present invention
A floppy disk using carbon black having a lower oil absorption instead of the component (Comparative Example 1) and a floppy disk using a fatty acid having a higher mp instead of the component (3) of the present invention have a dynamic friction coefficient of: In contrast to immediately after the start of the measurement, the value became significantly larger 100 or 200 minutes later, whereas the floppy disk disk (Examples 1 to 4), which is the magnetic recording medium of the present invention, was subjected to any of the environments of 60 ° C. and 5 ° C. Even with little change in dynamic friction coefficient with time, good lubricity, and greatly improved durability, by using a specific carbon black and a specific higher fatty acid or fatty acid ester in combination, even under environmental changes It can be seen that a magnetic recording medium having excellent durability can be obtained.

[0042]

According to the magnetic recording medium of the present invention, the magnetic layer is hardly worn and has excellent durability against environmental changes.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/708 G11B 5/71

Claims (1)

(57) [Claims] 1. A magnetic recording medium comprising a substrate and a magnetic layer containing a magnetic powder and a binder, 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 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.