JPS62219327A - Solid additive for magnetic recording medium and magnetic recording medium using such additive - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a solid additive for magnetic recording media and a magnetic recording medium using this solid additive, and more specifically, to a solid additive for magnetic recording media with excellent dispersibility. The present invention relates to a solid additive and a magnetic recording medium with excellent durability and surface smoothness obtained using the solid additive.

[Conventional technology]

In general, magnetic recording media, which are made by coating a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components on a substrate such as a polyester film, come into violent sliding contact with magnetic heads, etc. during recording and playback. The magnetic layer is easily abraded, and a magnetic layer with low abrasion and excellent durability is required.

Therefore, as a measure to improve the wear resistance of the magnetic layer, solid additives made of relatively hard non-magnetic powder are mixed into the magnetic layer. For example, at-Fe20
3 powder, Al2O3 powder, Cr2O3 powder, TiN powder, and SiC powder are mixed into the magnetic layer. (Japanese Patent Publication No. 58-45088, JP-A No. 56-13525) [Problems to be Solved by the Invention] However, these solid additive cuttings made of non-magnetic powder have poor dispersibility in the binder resin in the magnetic layer. Therefore, if a relatively large amount is mixed into the magnetic layer in an attempt to sufficiently improve the wear resistance of the magnetic layer, there is a problem that the surface smoothness of the magnetic layer cannot be sufficiently improved, and in particular, it is difficult to improve the recording density. Therefore, when using very fine magnetic powder and desiring to make the surface of the magnetic layer as smooth as possible, these solid additives with poor dispersibility may reduce the surface smoothness of the magnetic layer. However, the disadvantage is that it has a negative effect on the electrical characteristics.

[Means for solving problems]

This invention was made as a result of intensive research in view of the current situation, and the magnetic layer has an oriented shape, a maximum particle size of 0.01 to 2.0 μm, and a single molecule per unit surface area. By including a solid additive made of non-magnetic powder with an adsorption amount of layer water molecules of 2 to 4 molecules/nm', the dispersibility of the solid additive in the binder resin can be sufficiently improved, and particularly fine magnetic powder can be obtained. The surface smoothness of the magnetic layer used in the magnetic layer is improved, and the wear resistance of the magnetic layer is sufficiently improved without adversely affecting the electrical characteristics.

The solid additive used in this invention has an oriented shape, a maximum particle size of 0.01 to 2.0 μm, and an adsorption amount of monolayer water molecules per unit surface area of 2 to 4 molecules/n.
The magnetic layer contains a solid additive made of non-magnetic powder, which is preferably a non-magnetic powder with a monolayer water molecule adsorption amount of 2 to 4 molecules/nm per unit surface area with such fine particles. As a result, the amount of hydrophilic groups on the surface of the solid additive particles, such as O)-based groups, which are responsible for the binding force with the binder resin, and the polar groups in the binder resin are controlled to an appropriate amount. , these bond well with each other in appropriate proportions. Therefore, the solid additives are well captured in the binder resin and bonded well to the binder resin, thereby sufficiently improving the dispersibility and the surface smoothness of the magnetic layer. Moreover, this fine non-magnetic powder exhibits a sufficiently good polishing action, and the durability is sufficiently improved without adversely affecting the electrical characteristics.

In particular, the finer the solid additives used as dispersed in the binder resin in the magnetic layer, the more water molecules are adsorbed to the surface of the particles (and the more water molecules are bound to the binder resin). This effect is greater when fine solid additives are used together with fine magnetic powder, and the maximum particle size is 0.01 to 2.0 μm.
If the amount of water molecules adsorbed in a monomolecular layer per unit surface area of a fine solid additive exceeds 4 molecules/nrd, a large amount of solvent will be consumed to form a coating, and sufficient crosstalk conditions will not be obtained. , the dispersibility decreases, the surface smoothness of the magnetic layer deteriorates, and the electromagnetic conversion characteristics are adversely affected. Also, the amount of water molecules adsorbed in a monomolecular layer per unit surface area of the solid additive is 2 molecules/n, ? When the amount is less, the interaction with the binder resin becomes weaker and the surface smoothness of the magnetic layer deteriorates.

In addition, when the maximum particle size of the solid additive is larger than 2.0 μm, even if the amount of monolayer water molecules adsorbed to the unit surface area is more than 4 molecules/nd, the effect on kneading is not so significant. Although this is not a problem, if the particle size is too large, the surface smoothness of the magnetic layer cannot be sufficiently improved, and if the particle size is smaller than 0.01 μm, the polishing effect cannot be sufficiently exhibited, and the wear resistance of the magnetic layer cannot be sufficiently improved. Since it cannot be improved, 0.01~
It is preferable to use one within the range of 2.0 μm. Furthermore, even if solid additives with strong binding properties with the binder resin are used, non-oriented additives such as spherical or dice-shaped additives have poor filling properties in the magnetic layer. Since the surface amount also has a negative effect on lubricity, it is preferable to have an oriented shape such as a plate shape or a needle shape.

In this way, solid additives that are fine particles and have a monomolecular layer water molecule adsorption amount of 2 to 4 molecules/n'f per unit surface area, because the finer the solid additive is, the greater the amount of water adsorption on the particle surface. Usually, by making part of the particle surface of the solid additive hydrophobic, the amount of surface water adsorption is reduced and optimized.

Methods for making the particle surface of such solid additives hydrophobic include (1) surface treatment with an organic coupling agent, and (2) surface treatment with an inorganic hydrophobic coating such as a silica coating treated at high temperature. Basically, any method may be used, but it is generally preferable to use a surface treatment agent and a surface treatment method that do not easily separate from the particle surface of the solid additive.

In this way, the maximum particle size is 0.01 to 2.0 μm, and the amount of monolayer water molecules adsorbed to a unit surface area is 2 to 4 molecules per unit surface area.
Examples of solid additives that are within the nm range include oxide powders such as Al2O3 powder, Cr2O3 powder, Ti02 powder, 5i02 powder, and ct-Fe203 powder, carbide powders such as SiC powder, and TiN powder. Nitride powders and the like are preferably used. The amount of solid additives with a maximum particle diameter of 0.01 to 2.0 μm and a monomolecular layer water molecule adsorption amount of 2 to 4 molecules/nM per unit surface area is 0. If it is less than .5% by weight, the abrasion resistance will not be sufficiently improved, and if it is more than 20% by weight, it may lead to deterioration of the surface smoothness of the magnetic layer.
It is preferably contained in the magnetic layer in an amount of 0.5 to 20% by weight, more preferably 1 to 10% by weight.

The magnetic recording medium of the present invention may be manufactured according to a conventional method. A magnetic paint is prepared by mixing and dispersing a solid additive made of non-magnetic powder with a molecular adsorption amount of 2 to 4 molecules/nm together with magnetic powder, binder resin, organic solvent, etc., and this is applied to a substrate such as a polyester film. What is necessary is just to apply|coat on top by arbitrary coating means, such as a roll coater, and to dry.

Here, as the magnetic powder, for example, r-Fe203
powder, Fe3O4 powder, Co-containing r-Fe203 powder,
In addition to CO-containing Fe3O4 powder and CrO2 powder, various conventionally known magnetic powders such as Fe powder, Co powder, Fe-Ni powder, and barium ferrite powder are widely used.

In addition, binder components include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane resins, polyester resins, epoxy resins, polyamide resins, acrylic resins, isocyanate compounds, radiation-curable resins, etc. , which are commonly used as binder components in magnetic powders, are widely used.

Furthermore, as organic solvents, methyl isobutyl ketone,
Commonly used organic solvents such as ketone solvents such as methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate, alcohol solvents such as isopropyl alcohol, and aromatic hydrocarbon solvents such as toluene may be used alone or in combination. The above-mentioned mixtures are used, and as the substrate, any commonly used substrate can be used, such as synthetic resins such as polyester and polyamide cellulose derivatives, non-magnetic metals, films such as paper, and sheets.

In addition, various additives commonly used in magnetic paints,
For example, an antistatic agent such as carbon black, a lubricant, a dispersant, etc. may be optionally added.

〔Example〕

Next, embodiments of the invention will be described.

Examples 1 to 4 Using magnetic powder and non-magnetic powder shown in Table 1, magnetic powder 100 parts by weight VACH
(Manufactured by U, C, C, vinyl chloride 10-vinyl acetate-
(vinyl alcohol copolymer) Pandex T-5201 (large 6 〃manufactured by Nippon Ink Chemical Industry Co., Ltd., polyurethane resin, molecular weight 20,000 to 30,000) myristic acid 5 〃H3-5
00 (manufactured by Asahi Denka Co., Ltd., force 1〃-Bonburasoku) Non-magnetic powder 1~Cyclohexanone 85〃Toluene
The composition No. 85 was placed in a 31-capacity steel ball mill and rotated for 72 hours to ensure good dispersion to prepare a magnetic paste. Thereafter, this magnetic paste was coronated with 40 parts by weight of toluene, and
2 parts by weight of a trifunctional low molecular weight isocyanate compound (trifunctional low molecular weight isocyanate compound) was further added to cleave the magnetic paint. Apply this magnetic paint to a thickness of 1
It was coated on a 2 μm polyester base film to a coating thickness of 4 μm after drying, and dried to form a magnetic layer.

Next, the tape was mirror-finished and cut into 1/2-inch widths to produce magnetic tapes.

Comparative Examples 1 to 8 In the composition of the magnetic paint in Examples 1 to 4, the same amounts of magnetic powder and nonmagnetic powder shown in Table 2 were used instead of the magnetic powder and nonmagnetic powder shown in Table 1. Magnetic tapes were made in the same manner as in Examples 1-4.

Regarding the magnetic tape obtained in each example and comparative example,
Durability and surface smoothness were examined. Durability is commercially available VT
The determination was made by measuring the time until the output decreases by 3 dB when still images are reproduced in a constant temperature room at −5° C. using R. In addition, the surface smoothness was measured using a stylus roughness meter with a stylus speed of 0.06 cm/sec and a cutoff of 0.08 m.
The surface roughness (C, L, A) of the magnetic layer was measured under the conditions of m, and the relative values calculated according to the following formula using the magnetic tape of Example 1 as a reference were determined.

Table 3 below shows the results.

Table 3 [Effects of the Invention] As is clear from Table 3 above, the magnetic tapes obtained in Examples 1 to 4 have higher durability than the magnetic tapes obtained in Comparative Examples 1 to 8. As a result, the solid additive of the present invention has good dispersibility in the binder resin, and as a result, the magnetic recording medium obtained using this solid additive has a surface smoothness of the magnetic layer. It can be seen that the smoothness is good and the electrical properties and durability are improved.

Claims (1)

[Claims] 1. Has an oriented shape and has a maximum particle size of 0.01 to 2.0
In μm, the amount of water molecules adsorbed in a monomolecular layer per unit surface area is 2 to 4.
Solid additive 2 for magnetic recording media made of non-magnetic powder of molecule/nm^2, which has an oriented shape in the magnetic layer and has a maximum particle size of 0.
A magnetic material characterized by containing a solid additive for magnetic recording media consisting of a non-magnetic powder having a diameter of 01 to 2.0 μm and an adsorption amount of monolayer water molecules per unit surface area of 2 to 4 molecules/nm^2. recoding media