JPH03185624A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve mechanical characteristics and electric characteristics of a magnetic recording medium by allowing a small amt. of spherical solid additive to be omnipresent in the vicinity of the surface of the magnetic layer. CONSTITUTION:The spherical solid additive of <=1mum mean particle size is allowed to be omnipresent in the vicinity of the surface of the magnetic layer. Namely, in the spherical solid additive having <=1mum average particle size, the wearing amount of a magnetic head is smaller than that of an aspherical and squarish solid additive, and the wearing amount of a head can be properly suppressed even when a considerable amt. of the additive is distributed on the surface of magnetic layer. Since the shape of the additive is spherical real contact area between the solid additive and the magnetic head can be reduced to insure the good traveling property. Thereby, the recording medium excellent in mechanical characteristics and electric characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium and a method for manufacturing the same, and more particularly to a magnetic recording medium with excellent mechanical and electrical properties and a method for manufacturing the same.

[Conventional technology]

In general, magnetic recording media, which are made by coating and drying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components on a substrate, have a magnetic layer that comes into violent sliding contact with a magnetic head, etc. during recording and reproduction. Therefore, there is a need for a magnetic layer with low wear and excellent durability.

For this reason, large amounts of non-magnetic solid additives such as alumina, chromium oxide, and α-iron oxide have traditionally been added to the magnetic layer.Especially in floppy disks, these non-magnetic solid additives are A total amount of 20% by weight or more may be added to the magnetic powder in the magnetic layer. However, adding a large amount of nonmagnetic material to the magnetic layer inevitably results in
This results in a decrease in the magnetic properties of the magnetic recording medium, particularly a decrease in the saturation magnetization and squareness, and an accompanying significant deterioration in the electrical properties.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the various drawbacks of the conventional art and thereby provide a magnetic recording medium with excellent mechanical and electrical properties.

[Means to solve the problem]

That is, the present invention does not uniformly disperse a large amount of non-spherical and angular solid additives in the magnetic layer as in the conventional method, but instead makes a small amount of spherical solid additives unevenly distributed near the surface of the magnetic layer. As a result, the mechanical properties and electrical properties of the magnetic recording medium are sufficiently improved.

The solid additive used in this invention has an average particle size of ltI
It is preferable to use spherical solid additives with an average particle size of 1 μm or less and spherical particles unevenly distributed near the surface of the magnetic layer, and spherical solid additives with an average particle size of 1 μm or less have a higher magnetic The amount of polishing of the head is significantly small, and even if a considerable amount is disposed on the surface of the magnetic layer, the amount of polishing of the magnetic head is moderately suppressed. In addition, since the shape is spherical, solid additives and magnetic
...The actual contact area with the throat is extremely small, and the contact resistance between the magnetic layer and the magnetic head is also much lower than when using conventional non-spherical and angular solid additives. It is possible to ensure good driving characteristics. On the other hand, if the average particle size of the solid additive exceeds 1 μm, it is not preferable because the amount of abrasion of the magnetic gutter and the damage to the magnetic gutter become significant.

The solid additive preferably has a Mohs hardness of 8 or more; if the Mohs hardness is less than 8, the polishing ability of the magnetic head is insufficient, resulting in frequent head clogging.

Such uneven distribution of solid additives near the surface of the magnetic layer is caused by dispersing the solid additives in a solution of an organic hydrophobizing agent such as a hydrocarbon-based hydrophobizing agent or a fluoride-based hydrophobizing agent. This is done by chemically adsorbing a hydrophobizing agent on the surface of the solid additive and lowering its surface energy. A large difference in energy occurs, and this large difference in interfacial energy acts as a driving force, causing the solid additive to float in the magnetic paint, resulting in
Solid additives are unevenly distributed near the surface of the magnetic layer.

Here, as the hydrophobic treatment agent, coupling agents such as silane-based, titanate-based, aluminum-based, etc., which have excellent chemical adsorption properties on the solid additive surface, or hydrophobic treatment agents such as organosilazane are suitable. used.

When treated with a hydrophobic treatment agent to lower the surface energy and make the solid additives unevenly distributed near the surface of the magnetic layer, the mechanical properties of the magnetic recording medium will change depending on the amount of solid additives near the surface of the magnetic layer. Because of the almost determined relationship, the mechanical properties can be further improved, especially when the magnetic layer of a video tape or floppy disk comes into sliding contact with a magnetic head at high speed. This effect is significant because the mechanical properties are largely controlled by the behavior of . In addition, by unevenly distributing the solid additive near the surface of the magnetic layer, the amount of solid additive added to the magnetic layer can be reduced to less than half compared to the conventional method of uniformly dispersing the solid additive in the magnetic layer. Because it can reduce
The decrease in saturation magnetization and squareness of the magnetic recording medium due to the addition of solid additives can be significantly reduced compared to the conventional method, and the electrical properties are significantly improved.

In this way, when the solid additives are unevenly distributed near the surface of the magnetic layer, the mechanical properties and electrical properties are further improved. When there is little or no interaction with the resin, solid additives exposed on the surface of the magnetic layer may fall off from the surface of the magnetic layer as the magnetic recording medium runs. Therefore, in such cases, a binder resin containing a bond capable of electron beam crosslinking such as a C=C bond or a C-Cl bond in its molecule is used as the binder resin. =C bond or C-C1
It is preferable to chemically fix a C-C bond, which can be easily crosslinked with a bond by an electron beam, on the surface of a solid additive in advance, and a magnetic material containing such a binder resin and a solid additive. If the paint is applied onto the substrate, solid additives are unevenly distributed near the surface of the magnetic layer, and then irradiated with an electron beam,
A solid additive that is exposed on the surface of the magnetic layer and comes into direct contact with a magnetic head or the like can be firmly fixed to the surface of the magnetic layer.

Here, the chemical fixation of the C=C bond on the surface of the solid additive can be achieved by using a hydrophobizing agent containing a C-C bond during the hydrophobizing treatment of the solid additive, or by using a hydrophobizing agent and a C-C bond. This can be easily achieved by using a surface treatment agent containing a C bond in combination.

As long as the solid additive treated with the hydrophobic treatment agent is spherical, has an average particle size of 1 μm or less, and has a Mohs hardness of 8 or more, it can be used as a conventionally known solid additive.
may be used without any restriction, for example Alz 03 ,
Crz 03.3Aj! z○.

・Oxides such as 2SiO□, A-poor 2Ch ・TiO□, or TiB, , ZrB, , TiC, TiN
Non-oxides such as are preferably used. When used, these may be used alone or in combination of two or more. Further, the amount used is preferably within the range of 2 to 15% by weight based on the magnetic powder in the magnetic layer in order to sufficiently improve mechanical properties and electrical properties.

The magnetic recording medium of the present invention may be manufactured according to a conventional method, such as using a spherical solid additive treated with the hydrophobic treatment agent, having an average particle size of 1 μm or less, and a Mohs hardness of 8 or more. is mixed and dispersed with magnetic powder, binder resin, organic solvent, and other additives to prepare a magnetic paint, which is applied onto the surface of a substrate such as a polyester film by any means such as spraying or roll coating. and dry it.

Examples of magnetic powder include γ-Fe and O.

Powder, Fe:+04 powder, Co-containing 7-Fe, 03 powder, Co-containing Fe=○, powder, Cry, powder, as well as various conventionally known magnetic powders such as metal powders such as Fe powder and Co powder, and barium ferrite. Broadly encompassing.

As the binder resin, any binder resin normally used for magnetic recording media can be used, such as vinyl chloride-vinyl acetate copolymer, polyvinyl butyral resin, cellulose resin, polyurethane resin, and isocyanate compound. are also preferably used.

Furthermore, as organic solvents, methyl isobutyl ketone,
Commonly used materials such as methyl ethyl ketone, cyclohexanone toluene, ethyl acetate, tetrahydrofuran, dioxane, and dimethyl formamide are not particularly limited, and may be used alone or in combination of two or more.

In addition, in the magnetic paint, dispersants, lubricants, antistatic agents, and other substances that are generally added to magnetic paints may be added as necessary.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Spherical alumina (average particle size 0.2 100 parts by weight μm1
Mohs hardness 9) Hydrophobizing agent 2 (C4Hzt
S i (NH) 27□〉Methyl isobutyl ketone
60〃Toluene 60〃The above &11 precepts were mixed and dispersed in a pebble mill for about 100 hours to prepare an alumina dispersion mixture, and then this alumina dispersion mixture was filtered and dried to reduce the surface energy. Obtained alumina.

Next, using alumina whose surface energy has been lowered, 100 parts by weight of Co-containing 7-FezO+ (BE
T-specific surface area: 40 volts/g, magnetic cuff: 50 oersted) VAGH (manufactured by U, C, C Co., Ltd., vinyl chloride 12.5 〃Nyl-vinyl acetate-vinyl alcohol copolymer) T-5250 (Dainippon Ink Co., Ltd.) 7. 5 Polyurethane resin manufactured by Gaku Kogyo Co., Ltd.) Coronate L (manufactured by Nippon Polyurethane Co., Ltd. 5 Trifunctional low molecular weight isocyanate compound manufactured by Gaku Kogyo Co., Ltd.) Spheres with reduced surface energy 4 Alumina myristic acid 3 Cyclohexanone 100 Toluene
A magnetic coating material was prepared by mixing and dispersing the composition No. 100 in a ball mill for about 100 hours. Next, this magnetic paint was applied onto a polyester film with a thickness of I3 μm so that the thickness of the dried coating was approximately 4 μm, and after mirror treatment, the magnetic tape was cut into a predetermined width. Had made.

Comparative Example 1 In the composition of the magnetic paint in Example 1, the same amount of untreated spherical alumina was used instead of the spherical alumina whose surface energy was lowered by the hydrophobizing agent.
A magnetic tape was made in the same manner as in Example 1.

Comparative Example 2 The composition of the magnetic paint in Example 1 was the same as in Example 1 except that 10 parts by weight of untreated spherical alumina was used in place of the spherical alumina whose surface energy had been lowered by the hydrophobizing agent. and made magnetic tape.

Comparative Example 3 In the composition of the magnetic paint in Example 1, instead of the spherical alumina whose surface energy was reduced by the hydrophobizing agent, non-spherical angular alumina whose surface energy was similarly reduced (average particle size 0.2μm, Mohs hardness 9)
A magnetic tape was made in the same manner as in Example 1, except that the same amount of .

Comparative Example 4 In the composition of the magnetic paint in Example 1, untreated non-spherical angular alumina (average particle size 0.2 μm, Mohs hardness 9 A magnetic tape was produced in the same manner as in Example 1, except that 10 parts by weight of 1.

Regarding the magnetic tapes obtained in each example and comparative example,
Still durability at -10°C, 1o.

The wear amount of the magnetic head after running for hours, the durability after running 100 times, and the output at 8 MHz were investigated. Durability when running 100 times is when the magnetic layer is not scratched at all after 100 runs (◎), and when the magnetic layer has traces of running the magnetic head but the output does not deteriorate (○). A case where the magnetic layer was scratched was evaluated as (x).

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the magnetic tape obtained by the present invention (Example 1) has a higher magnetic head than the magnetic tape obtained in Comparative Examples 1 to 4. The amount of abrasion is small, the still durability is good, the durability after running 100 times is high, and the output is high.This shows that the magnetic recording medium obtained by this invention has excellent mechanical and electrical properties. .

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that a spherical solid additive with an average particle size of 1 μm or less is unevenly distributed near the surface of the magnetic layer. 2. The solid additive is Al_2O_3 with a Mohs hardness of 8 or more.
, Cr_2O_3, 3Al_2O_3・2SiO_2,
Oxides such as Al_2O_3 and TiO_2, or T
The magnetic recording medium 3 according to claim 1, which is a non-oxide such as iB_2, ZrB_2, TiC, TiN, etc., is treated by treating a spherical solid additive with an average particle size of 1 μm or less with an organic hydrophobizing agent. After preparing a magnetic paint by mixing and dispersing the solid additives together with magnetic powder, binder components, organic solvents, and other necessary components,
This magnetic paint is applied onto the substrate, dried, and the average particle size is 1.
Method 4 for producing a magnetic recording medium characterized by forming a magnetic layer in which spherical solid additives of μm or less are unevenly distributed near the surface, the solid additive is Al_2O_3 with a Mohs hardness of 8 or more
, Cr_2O_3, 3Al_2O_3・2SiO_2,
Oxides such as Al_2O_3 and TiO_2, or T
The method for manufacturing a magnetic recording medium according to claim 3, wherein the magnetic recording medium is a non-oxide such as iB_2, ZrB_2, TiC, or TiN.