JPH01201822A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance the durability, wear resistance and surface smoothness of a medium and to decrease the wear of a magnetic head by incorporating inorg. powder having specific pH, particle size and hardness into a magnetic layer. CONSTITUTION:The inorg. powder (A) having <7pH, <=1mum average grain size and >=6 Mohs hardness and magnetic powder (e.g.: Co-deposited gamma-Fe2O3) are incorporated into the magnetic layer of the title medium. The pH of said powder A can be adjusted to <7 by a method of immersing the inorg. powder into a soln. of an inorg. acid, etc., and drying the powder. The dispersion in the coating liquid increases and the dislodgment of the powder from the coated film increases if the pH is >=7. The surface smoothness of the magnetic layer degrades if the grain size exceeds the above-mentioned range. The powder is inadequate as a polishing agent if the hardness is below the above-mentioned range. The use of alumina as the powder A is possible.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to magnetic recording media.

More specifically, the present invention relates to a magnetic recording medium whose magnetic layer has excellent abrasion resistance, durability, and surface smoothness, and whose magnetic head has an improved abrasion suppressing effect.

<Prior Art> Magnetic recording media such as magnetic tapes, magnetic disks, and magnetic sheets are widely used for audio, video, and computers.

In such magnetic recording media, non-magnetic powder with a Mohs hardness of 6 or more selected from AjlzOs, Cr, O, cr-Fe20s, etc. is used as an abrasive to improve the durability and wear resistance of the magnetic layer. It is added as.

However, while the addition of these abrasives improves durability and wear resistance, it also reduces the surface smoothness of the magnetic layer, deteriorating the electromagnetic characteristics, and causing some of the added abrasives to detach. The head may become worn out or the magnetic head may become clogged.
This had the disadvantage of causing an increase in noise.

In particular, in recent years, metal magnetic powder or fine magnetic powder has been used to form the magnetic layer to achieve higher density magnetic recording. This has exacerbated the disadvantages that the magnetic layer's durability and abrasion resistance are reduced, leading to increased deterioration of electromagnetic transducability, increased wear and tear on the head due to detachment of the abrasive material, and further deterioration of the durability and wear resistance of the magnetic layer.

In order to solve these problems, methods of adding dispersants such as fatty acids, fatty acid esters, phosphate esters, and surfactants have been proposed.

However, even if these dispersants are added, if the amount added is small, the dispersion of the abrasive is insufficient, and if the amount added is too large, the dispersant oozes out, which is undesirable.

Furthermore, a method using an abrasive treated with a coupling agent such as a silane coupling agent or a titanium coupling agent has been proposed.

However, these coupling agents tend to come off from the abrasive material when dispersing the magnetic paint, and the dispersion effect is insufficient.

(Problems to be Solved by the Invention) In view of the above circumstances, the present inventors have conducted extensive studies with the aim of obtaining a magnetic recording medium that has excellent durability, abrasion resistance, and surface smoothness, and has less wear and tear on the magnetic head. As a result, the present inventors discovered that a magnetic recording medium that satisfies all of the above objectives can be obtained when inorganic powder having specific physical properties is used, and the present invention has been completed.

(Means for Solving the Problems) That is, the present invention provides a magnetic recording medium having a magnetic layer containing an inorganic powder having a pH of less than 7 and an average particle diameter of 1 μm or less and a Mohs hardness of 6 or more and a magnetic powder. It is in.

The present invention will be explained in more detail below.

pH of inorganic powder used in the present invention (JISR612
9-1976) is less than 7, preferably 6
．． It is essential to set it to 5 or less.

When the pH of the inorganic powder becomes 7 or more, the dispersion in the magnetic coating becomes insufficient, and the inorganic powder is often detached from the magnetic coating, resulting in a decrease in the surface smoothness of the magnetic layer. , the electromagnetic conversion characteristics deteriorate, the wear and tear of the head increases, causing clogging of the magnetic head and an increase in noise.

The method of making the inorganic powder less than pH 7 is not particularly limited as long as the inorganic powder after treatment has a pH of less than 7, but usually, after immersion in a solution of an inorganic acid or an organic acid, The methods used include filtration and drying, or evaporation, coating, and drying.

The inorganic acids used include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, chlorosulfonic acid, etc., and the organic acids include formic acid,
Examples include monocarboxylic acids such as acetic acid, monochloroacetic acid, trichloroacetic acid, and propionic acid; dicarboxylic acids such as oxalic acid, fumaric acid, maleic acid, and succinic acid; and sulfonic acids such as benzenesulfonic acid.

Next, the inorganic powder used in the present invention has an average particle diameter of 1
It is necessary to make the thickness less than μm, preferably less than 0.8 μm.

If it is 1 μm or more, the surface smoothness of the magnetic layer will deteriorate, which is not preferable.

Examples of such inorganic powders include those having a Mohs hardness of 6 or more, such as alumina, α-iron oxide, and spinel.

If the Mohs hardness is less than 6, it is not desirable as an abrasive.

In particular, alumina is particularly preferred because of its high polishing performance (and good dispersibility).

The addition ratio of the abrasive to the magnetic powder is generally 0.1 to 1.
5% by weight, preferably 0.5-10% by weight. If the amount of abrasive added is less than 0.1% by weight, the durability and abrasion resistance of the magnetic layer will decrease;
If the amount increases, wear and tear on the magnetic head increases, which is not preferable.

The magnetic material used in the present invention may be a known magnetic material such as rFez 03 or Co-containing T-FezO.
s, Co deposition 1 F ez 03 , F e.

Oa, Co-containing Fes O4, CO-coated Fe, Oa
, Cr 02 and other oxide magnetic materials, such as Fe, Ni
s C0% Fe-Ni alloy, Fe-Co alloy, Fe-
N1-P alloy, Fe-Nt-Co alloy, Fe-Mn-Z
n alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-C
r alloy, )”e-Co-Ni-P alloy, Co-Ni alloy, Co-P alloy, Co-Cr alloy, etc., Fe%N
i % Various magnetic materials such as metal magnetic powder mainly composed of Co are used. The particle size is not particularly limited, but
Generally, those having a diameter in the range of 0.05 to 5 μm are used.

Additives to these magnetic materials include Si%C
u%Zn%A Elements such as 1, P, Mn, Or, or compounds thereof may be contained.

It is also possible to contain hexagonal ferrite such as barium ferrite and iron nitride.

As the binder used in the magnetic layer of the present invention, a thermoplastic resin, a thermosetting resin, a reactive resin, an electron beam curable resin, or a compound thereof is used.

Examples of such binders include urethane resins, epoxy resins, urea resins, amide resins, silicone resins, polyester resins, phenol resins, vinyl resins, cellulose derivatives, rubber resins, etc., singly or in mixtures.

<Effects of the Invention> As detailed above, in the present invention, by using an extremely simple method of using an inorganic powder having a Mohs hardness of 6 or more, an average particle size of 1 μm or less, and a pH of less than 7 as an abrasive for forming a magnetic layer, The magnetic layer has excellent durability, smoothness and wear resistance,
The present invention has made it possible to provide a magnetic recording medium in which the effect of suppressing wear and damage of the magnetic heald has been improved, and its industrial value is extremely great.

(Examples) The present invention will be described in more detail below using examples.

Example 1 α 'It 03 (A
A magnetic paint was prepared using 0.5 parts by weight of α-A2 of PH6.0 obtained by immersing KP30 (manufactured by Sumitomo Chemical Co., Ltd.) in an aqueous hydrochloric acid solution and drying it at the following weight mixing ratio.

CO deposition r Fezes 100 parts by weight BET
Specific surface area 43mr/gHe
7800e65 P m u / g Long axis 0.25 μm Short axis 0.05 μm Polyurethane resin 10 parts by weight Nitrocellulose
10 layer carbon black
4 parts by weight Butyl stearate 1 part by weight Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Cyclohexanone
50 parts by weight of the above composition in an attritor
After time dispersion, it was dispersed in a ball mill for 2 hours, 4 parts by weight of polyisocyanate curing agent was added, filtered through a filter with an average diameter of 1 μm, and then placed on a 10 μm thick polyethylene terecrate film so that the magnetic N thickness was 5 μm. The magnetic tape was coated, dried, cured after calendering, and cut into a predetermined width to produce a magnetic tape.

Examples 2 to 9 and Comparative Examples 1 to 5 α-AIlzOs as the inorganic powder of Example 1 was
A magnetic tape was produced in the same manner as in Example 1 except that the inorganic powder shown in the table was used.

After loading the magnetic tape obtained in each example and comparative example into a video tape recorder and running it for 100 hours, the amount of wear of the magnetic head (Sendust) of the video tape recorder and still characteristics (no blurring of still images) The time required for confirmation was measured. In addition, the tape surface was measured with a surface roughness meter to determine the center line average roughness.

The results are shown in Table 1.

Claims (1)

[Claims] (1) A magnetic recording medium having a magnetic layer comprising an inorganic powder having a pH of less than 7, an average particle diameter of 1 μm or less, and a Mohs hardness of 6 or more, and a magnetic powder.